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<?php
/**
* Class to wrap "is_email" function by  Dominic Sayers
* and a few other email related methods that shouldn't be in the main module class
* Added by Jo Morg
*/
/**
 * To validate an email address according to RFCs 5321, 5322 and others
 * 
 * Copyright © 2008-2011, Dominic Sayers          <br>
 * Test schema documentation Copyright © 2011, Daniel Marschall      <br>
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 
 *     - Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *     - Redistributions in binary form must reproduce the above copyright notice,
 *       this list of conditions and the following disclaimer in the documentation
 *       and/or other materials provided with the distribution.
 *     - Neither the name of Dominic Sayers nor the names of its contributors may be
 *       used to endorse or promote products derived from this software without
 *       specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * @package  is_email
 * @author  Dominic Sayers <dominic@sayers.cc>
 * @copyright  2008-2011 Dominic Sayers
 * @license  http://www.opensource.org/licenses/bsd-license.php BSD License
 * @link  http://www.dominicsayers.com/isemail
 * @version  3.01.1 - Fixed examples and readme.txt
 */

// The quality of this code has been improved greatly by using PHPLint
// Copyright (c) 2010 Umberto Salsi
// This is free software; see the license for copying conditions.
// More info: http://www.icosaedro.it/phplint/
/*.
  require_module 'standard';
  require_module 'pcre';
.*/

if (!defined('ISEMAIL_VALID')) 
{
  /*:diagnostic constants start:*/
  
  // This part of the code is generated using data from test/meta.xml. Beware of making manual alterations
  // Categories
  define('ISEMAIL_VALID_CATEGORY', 1);
  define('ISEMAIL_DNSWARN', 7);
  define('ISEMAIL_RFC5321', 15);
  define('ISEMAIL_CFWS', 31);
  define('ISEMAIL_DEPREC', 63);
  define('ISEMAIL_RFC5322', 127);
  define('ISEMAIL_ERR', 255);

  // Diagnoses
  // Address is valid
  define('ISEMAIL_VALID', 0);
  // Address is valid but a DNS check was not successful
  define('ISEMAIL_DNSWARN_NO_MX_RECORD', 5);
  define('ISEMAIL_DNSWARN_NO_RECORD', 6);
  // Address is valid for SMTP but has unusual elements
  define('ISEMAIL_RFC5321_TLD', 9);
  define('ISEMAIL_RFC5321_TLDNUMERIC', 10);
  define('ISEMAIL_RFC5321_QUOTEDSTRING', 11);
  define('ISEMAIL_RFC5321_ADDRESSLITERAL', 12);
  define('ISEMAIL_RFC5321_IPV6DEPRECATED', 13);
  // Address is valid within the message but cannot be used unmodified for the envelope
  define('ISEMAIL_CFWS_COMMENT', 17);
  define('ISEMAIL_CFWS_FWS', 18);
  // Address contains deprecated elements but may still be valid in restricted contexts
  define('ISEMAIL_DEPREC_LOCALPART', 33);
  define('ISEMAIL_DEPREC_FWS', 34);
  define('ISEMAIL_DEPREC_QTEXT', 35);
  define('ISEMAIL_DEPREC_QP', 36);
  define('ISEMAIL_DEPREC_COMMENT', 37);
  define('ISEMAIL_DEPREC_CTEXT', 38);
  define('ISEMAIL_DEPREC_CFWS_NEAR_AT', 49);
  // The address is only valid according to the broad definition of RFC 5322. It is otherwise invalid.
  define('ISEMAIL_RFC5322_DOMAIN', 65);
  define('ISEMAIL_RFC5322_TOOLONG', 66);
  define('ISEMAIL_RFC5322_LOCAL_TOOLONG', 67);
  define('ISEMAIL_RFC5322_DOMAIN_TOOLONG', 68);
  define('ISEMAIL_RFC5322_LABEL_TOOLONG', 69);
  define('ISEMAIL_RFC5322_DOMAINLITERAL', 70);
  define('ISEMAIL_RFC5322_DOMLIT_OBSDTEXT', 71);
  define('ISEMAIL_RFC5322_IPV6_GRPCOUNT', 72);
  define('ISEMAIL_RFC5322_IPV6_2X2XCOLON', 73);
  define('ISEMAIL_RFC5322_IPV6_BADCHAR', 74);
  define('ISEMAIL_RFC5322_IPV6_MAXGRPS', 75);
  define('ISEMAIL_RFC5322_IPV6_COLONSTRT', 76);
  define('ISEMAIL_RFC5322_IPV6_COLONEND', 77);
  // Address is invalid for any purpose
  define('ISEMAIL_ERR_EXPECTING_DTEXT', 129);
  define('ISEMAIL_ERR_NOLOCALPART', 130);
  define('ISEMAIL_ERR_NODOMAIN', 131);
  define('ISEMAIL_ERR_CONSECUTIVEDOTS', 132);
  define('ISEMAIL_ERR_ATEXT_AFTER_CFWS', 133);
  define('ISEMAIL_ERR_ATEXT_AFTER_QS', 134);
  define('ISEMAIL_ERR_ATEXT_AFTER_DOMLIT', 135);
  define('ISEMAIL_ERR_EXPECTING_QPAIR', 136);
  define('ISEMAIL_ERR_EXPECTING_ATEXT', 137);
  define('ISEMAIL_ERR_EXPECTING_QTEXT', 138);
  define('ISEMAIL_ERR_EXPECTING_CTEXT', 139);
  define('ISEMAIL_ERR_BACKSLASHEND', 140);
  define('ISEMAIL_ERR_DOT_START', 141);
  define('ISEMAIL_ERR_DOT_END', 142);
  define('ISEMAIL_ERR_DOMAINHYPHENSTART', 143);
  define('ISEMAIL_ERR_DOMAINHYPHENEND', 144);
  define('ISEMAIL_ERR_UNCLOSEDQUOTEDSTR', 145);
  define('ISEMAIL_ERR_UNCLOSEDCOMMENT', 146);
  define('ISEMAIL_ERR_UNCLOSEDDOMLIT', 147);
  define('ISEMAIL_ERR_FWS_CRLF_X2', 148);
  define('ISEMAIL_ERR_FWS_CRLF_END', 149);
  define('ISEMAIL_ERR_CR_NO_LF', 150);
// End of generated code
/*:diagnostic constants end:*/

  // function control
  define('ISEMAIL_THRESHOLD'    , 16);

  // Email parts
  define('ISEMAIL_COMPONENT_LOCALPART'  , 0);
  define('ISEMAIL_COMPONENT_DOMAIN'  , 1);
  define('ISEMAIL_COMPONENT_LITERAL'  , 2);
  define('ISEMAIL_CONTEXT_COMMENT'  , 3);
  define('ISEMAIL_CONTEXT_FWS'    , 4);
  define('ISEMAIL_CONTEXT_QUOTEDSTRING'  , 5);
  define('ISEMAIL_CONTEXT_QUOTEDPAIR'  , 6);

  // Miscellaneous string constants
  define('ISEMAIL_STRING_AT'    , '@');
  define('ISEMAIL_STRING_BACKSLASH'  , '\\');
  define('ISEMAIL_STRING_DOT'    , '.');
  define('ISEMAIL_STRING_DQUOTE'    , '"');
  define('ISEMAIL_STRING_OPENPARENTHESIS'  , '(');
  define('ISEMAIL_STRING_CLOSEPARENTHESIS', ')');
  define('ISEMAIL_STRING_OPENSQBRACKET'  , '[');
  define('ISEMAIL_STRING_CLOSESQBRACKET'  , ']');
  define('ISEMAIL_STRING_HYPHEN'    , '-');
  define('ISEMAIL_STRING_COLON'    , ':');
  define('ISEMAIL_STRING_DOUBLECOLON'  , '::');
  define('ISEMAIL_STRING_SP'    , ' ');
  define('ISEMAIL_STRING_HTAB'    , "\t");
  define('ISEMAIL_STRING_CR'    , "\r");
  define('ISEMAIL_STRING_LF'    , "\n");
  define('ISEMAIL_STRING_IPV6TAG'    , 'IPv6:');
  // US-ASCII visible characters not valid for atext (http://tools.ietf.org/html/rfc5322#section-3.2.3)
  define('ISEMAIL_STRING_SPECIALS'  , '()<>[]:;@\\,."');
}

class email_validator
{
    /**
   * Check that an email address conforms to RFCs 5321, 5322 and others
   *
   * As of Version 3.0, we are now distinguishing clearly between a Mailbox
   * as defined by RFC 5321 and an addr-spec as defined by RFC 5322. Depending
   * on the context, either can be regarded as a valid email address. The
   * RFC 5321 Mailbox specification is more restrictive (comments, white space
   * and obsolete forms are not allowed)
   *
   * @param string  $email    The email address to check
   * @param boolean  $checkDNS  If true then a DNS check for MX records will be made
   * @param mixed    $errorlevel  Determines the boundary between valid and invalid addresses.
   *           Status codes above this number will be returned as-is,
   *           status codes below will be returned as ISEMAIL_VALID. Thus the
   *           calling program can simply look for ISEMAIL_VALID if it is
   *           only interested in whether an address is valid or not. The
   *           errorlevel will determine how "picky" is_email() is about
   *           the address.
   *
   *           If omitted or passed as false then is_email() will return
   *           true or false rather than an integer error or warning.
   *
   *           NB Note the difference between $errorlevel = false and
   *           $errorlevel = 0
   * @param array    $parsedata  If passed, returns the parsed address components
   */
  /*.mixed.*/ 
  public static function is_email($email, $checkDNS = false, $errorlevel = false, &$parsedata = array()) 
  {
    // Check that $email is a valid address. Read the following RFCs to understand the constraints:
    //   (http://tools.ietf.org/html/rfc5321)
    //   (http://tools.ietf.org/html/rfc5322)
    //   (http://tools.ietf.org/html/rfc4291#section-2.2)
    //   (http://tools.ietf.org/html/rfc1123#section-2.1)
    //   (http://tools.ietf.org/html/rfc3696) (guidance only)
    
    // version 2.0: Enhance $diagnose parameter to $errorlevel
    // version 3.0: Introduced status categories
    // revision 3.1: BUG: $parsedata was passed by value instead of by reference

    if (is_bool($errorlevel)) {
      $threshold  = ISEMAIL_VALID;
      $diagnose  = (bool) $errorlevel;
    } else {
      $diagnose  = true;

      switch ((int) $errorlevel) {
      case E_WARNING:  $threshold  = ISEMAIL_THRESHOLD;  break;  // For backward compatibility
      case E_ERROR:  $threshold  = ISEMAIL_VALID;  break;  // For backward compatibility
      default:  $threshold  = (int) $errorlevel;
      }
    }

    $return_status = array(ISEMAIL_VALID);

    // Parse the address into components, character by character
    $raw_length  = strlen($email);
    $context  = ISEMAIL_COMPONENT_LOCALPART;  // Where we are
    $context_stack  = array($context);    // Where we have been
    $context_prior  = ISEMAIL_COMPONENT_LOCALPART;  // Where we just came from
    $token    = '';        // The current character
    $token_prior  = '';        // The previous character
    $parsedata  = array(
          ISEMAIL_COMPONENT_LOCALPART  => '',
          ISEMAIL_COMPONENT_DOMAIN  => ''
               );      // For the components of the address

    $atomlist  = array(
          ISEMAIL_COMPONENT_LOCALPART  => array(''),
          ISEMAIL_COMPONENT_DOMAIN  => array('')
               );      // For the dot-atom elements of the address
    $element_count  = 0;
    $element_len  = 0;
    $hyphen_flag  = false;      // Hyphen cannot occur at the end of a subdomain
    $end_or_die  = false;      // CFWS can only appear at the end of the element

  //-echo "<table style=\"clear:left;\">"; // debug
    for ($i = 0; $i < $raw_length; $i++) {
      $token = $email[$i];
  //-echo "<tr><td><strong>$context|",(($end_or_die) ? 'true' : 'false'),"|$token|" . max($return_status) . "</strong></td>"; // debug

      switch ($context) {
      //-------------------------------------------------------------
      // local-part
      //-------------------------------------------------------------
      case ISEMAIL_COMPONENT_LOCALPART:
        // http://tools.ietf.org/html/rfc5322#section-3.4.1
        //   local-part      =   dot-atom / quoted-string / obs-local-part
        //
        //   dot-atom        =   [CFWS] dot-atom-text [CFWS]
        //
        //   dot-atom-text   =   1*atext *("." 1*atext)
        //
        //   quoted-string   =   [CFWS]
        //                       DQUOTE *([FWS] qcontent) [FWS] DQUOTE
        //                       [CFWS]
        //
        //   obs-local-part  =   word *("." word)
        //
        //   word            =   atom / quoted-string
        //
        //   atom            =   [CFWS] 1*atext [CFWS]
        switch ($token) {
        // Comment
        case ISEMAIL_STRING_OPENPARENTHESIS:
          if ($element_len === 0)
            // Comments are OK at the beginning of an element
            $return_status[]  = ($element_count === 0) ? ISEMAIL_CFWS_COMMENT : ISEMAIL_DEPREC_COMMENT;
          else {
            $return_status[]  = ISEMAIL_CFWS_COMMENT;
            $end_or_die    = true;  // We can't start a comment in the middle of an element, so this better be the end
          }

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_COMMENT;
          break;
        // Next dot-atom element
        case ISEMAIL_STRING_DOT:
          if ($element_len === 0)
            // Another dot, already?
            $return_status[] = ($element_count === 0) ? ISEMAIL_ERR_DOT_START : ISEMAIL_ERR_CONSECUTIVEDOTS;  // Fatal error
          else
            // The entire local-part can be a quoted string for RFC 5321
            // If it's just one atom that is quoted then it's an RFC 5322 obsolete form
            if ($end_or_die) $return_status[] = ISEMAIL_DEPREC_LOCALPART;

            $end_or_die  = false;  // CFWS & quoted strings are OK again now we're at the beginning of an element (although they are obsolete forms)
            $element_len  = 0;
            $element_count++;
            $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
            $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  = '';

          break;
        // Quoted string
        case ISEMAIL_STRING_DQUOTE:
          if ($element_len === 0) {
            // The entire local-part can be a quoted string for RFC 5321
            // If it's just one atom that is quoted then it's an RFC 5322 obsolete form
            $return_status[]  = ($element_count === 0) ? ISEMAIL_RFC5321_QUOTEDSTRING : ISEMAIL_DEPREC_LOCALPART;

            $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
            $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= $token;
            $element_len++;
            $end_or_die    = true;  // Quoted string must be the entire element
            $context_stack[]  = $context;
            $context    = ISEMAIL_CONTEXT_QUOTEDSTRING;
          } else {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_ATEXT;  // Fatal error
          }

          break;
        // Folding White Space
        case ISEMAIL_STRING_CR:
        case ISEMAIL_STRING_SP:
        case ISEMAIL_STRING_HTAB:
          if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;  break;}  // Fatal error

          if ($element_len === 0)
            $return_status[] = ($element_count === 0) ? ISEMAIL_CFWS_FWS : ISEMAIL_DEPREC_FWS;
          else
            $end_or_die = true;  // We can't start FWS in the middle of an element, so this better be the end

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_FWS;
          $token_prior    = $token;

          break;
        // @
        case ISEMAIL_STRING_AT:
          // At this point we should have a valid local-part
          if (count($context_stack) !== 1) die('Unexpected item on context stack');

          if  ($parsedata[ISEMAIL_COMPONENT_LOCALPART] === '')
                  $return_status[]  = ISEMAIL_ERR_NOLOCALPART;  // Fatal error
          elseif  ($element_len === 0)  $return_status[]  = ISEMAIL_ERR_DOT_END;  // Fatal error
          // http://tools.ietf.org/html/rfc5321#section-4.5.3.1.1
          //   The maximum total length of a user name or other local-part is 64
          //   octets.
          elseif  (strlen($parsedata[ISEMAIL_COMPONENT_LOCALPART]) > 64)
                  $return_status[]  = ISEMAIL_RFC5322_LOCAL_TOOLONG;
          // http://tools.ietf.org/html/rfc5322#section-3.4.1
          //   Comments and folding white space
          //   SHOULD NOT be used around the "@" in the addr-spec.
          //
          // http://tools.ietf.org/html/rfc2119
          // 4. SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
          //    there may exist valid reasons in particular circumstances when the
          //    particular behavior is acceptable or even useful, but the full
          //    implications should be understood and the case carefully weighed
          //    before implementing any behavior described with this label.
          elseif  (($context_prior === ISEMAIL_CONTEXT_COMMENT) || ($context_prior === ISEMAIL_CONTEXT_FWS))
                  $return_status[]  = ISEMAIL_DEPREC_CFWS_NEAR_AT;

          // Clear everything down for the domain parsing
          $context  = ISEMAIL_COMPONENT_DOMAIN;  // Where we are
          $context_stack  = array($context);    // Where we have been
          $element_count  = 0;
          $element_len  = 0;
          $end_or_die  = false;      // CFWS can only appear at the end of the element

          break;
        // atext
        default:
          // http://tools.ietf.org/html/rfc5322#section-3.2.3
          //    atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
          //                        "!" / "#" /        ;  characters not including
          //                        "$" / "%" /        ;  specials.  Used for atoms.
          //                        "&" / "'" /
          //                        "*" / "+" /
          //                        "-" / "/" /
          //                        "=" / "?" /
          //                        "^" / "_" /
          //                        "`" / "{" /
          //                        "|" / "}" /
          //                        "~"
          if ($end_or_die) {
            // We have encountered atext where it is no longer valid
            switch ($context_prior) {
            case ISEMAIL_CONTEXT_COMMENT:
            case ISEMAIL_CONTEXT_FWS:
              $return_status[]  = ISEMAIL_ERR_ATEXT_AFTER_CFWS;
              break;
            case ISEMAIL_CONTEXT_QUOTEDSTRING:
              $return_status[]  = ISEMAIL_ERR_ATEXT_AFTER_QS;
              break;
            default:
              die ("More atext found where none is allowed, but unrecognised prior context: $context_prior");
            }
          } else {
            $context_prior  = $context;
            $ord    = ord($token);

            if (($ord < 33) || ($ord > 126) || ($ord === 10) || (!is_bool(strpos(ISEMAIL_STRING_SPECIALS, $token))))
              $return_status[]  = ISEMAIL_ERR_EXPECTING_ATEXT;  // Fatal error

            $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
            $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= $token;
            $element_len++;
          }
        }

        break;
      //-------------------------------------------------------------
      // Domain
      //-------------------------------------------------------------
      case ISEMAIL_COMPONENT_DOMAIN:
        // http://tools.ietf.org/html/rfc5322#section-3.4.1
        //   domain          =   dot-atom / domain-literal / obs-domain
        //
        //   dot-atom        =   [CFWS] dot-atom-text [CFWS]
        //
        //   dot-atom-text   =   1*atext *("." 1*atext)
        //
        //   domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
        //
        //   dtext           =   %d33-90 /          ; Printable US-ASCII
        //                       %d94-126 /         ;  characters not including
        //                       obs-dtext          ;  "[", "]", or "\"
        //
        //   obs-domain      =   atom *("." atom)
        //
        //   atom            =   [CFWS] 1*atext [CFWS]


        // http://tools.ietf.org/html/rfc5321#section-4.1.2
        //   Mailbox        = Local-part "@" ( Domain / address-literal )
        //
        //   Domain         = sub-domain *("." sub-domain)
        //
        //   address-literal  = "[" ( IPv4-address-literal /
        //                    IPv6-address-literal /
        //                    General-address-literal ) "]"
        //                    ; See Section 4.1.3

        // http://tools.ietf.org/html/rfc5322#section-3.4.1
        //      Note: A liberal syntax for the domain portion of addr-spec is
        //      given here.  However, the domain portion contains addressing
        //      information specified by and used in other protocols (e.g.,
        //      [RFC1034], [RFC1035], [RFC1123], [RFC5321]).  It is therefore
        //      incumbent upon implementations to conform to the syntax of
        //      addresses for the context in which they are used.
        // is_email() author's note: it's not clear how to interpret this in
        // the context of a general email address validator. The conclusion I
        // have reached is this: "addressing information" must comply with
        // RFC 5321 (and in turn RFC 1035), anything that is "semantically
        // invisible" must comply only with RFC 5322.
        switch ($token) {
        // Comment
        case ISEMAIL_STRING_OPENPARENTHESIS:
          if ($element_len === 0)
            // Comments at the start of the domain are deprecated in the text
            // Comments at the start of a subdomain are obs-domain
            // (http://tools.ietf.org/html/rfc5322#section-3.4.1)
            $return_status[]  = ($element_count === 0) ? ISEMAIL_DEPREC_CFWS_NEAR_AT : ISEMAIL_DEPREC_COMMENT;
          else {
            $return_status[]  = ISEMAIL_CFWS_COMMENT;
            $end_or_die    = true;  // We can't start a comment in the middle of an element, so this better be the end
          }

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_COMMENT;
          break;
        // Next dot-atom element
        case ISEMAIL_STRING_DOT:
          if ($element_len === 0)
            // Another dot, already?
            $return_status[]  = ($element_count === 0) ? ISEMAIL_ERR_DOT_START : ISEMAIL_ERR_CONSECUTIVEDOTS;  // Fatal error
          elseif ($hyphen_flag)
            // Previous subdomain ended in a hyphen
            $return_status[]  = ISEMAIL_ERR_DOMAINHYPHENEND;  // Fatal error
          else
            // Nowhere in RFC 5321 does it say explicitly that the
            // domain part of a Mailbox must be a valid domain according
            // to the DNS standards set out in RFC 1035, but this *is*
            // implied in several places. For instance, wherever the idea
            // of host routing is discussed the RFC says that the domain
            // must be looked up in the DNS. This would be nonsense unless
            // the domain was designed to be a valid DNS domain. Hence we
            // must conclude that the RFC 1035 restriction on label length
            // also applies to RFC 5321 domains.
            //
            // http://tools.ietf.org/html/rfc1035#section-2.3.4
            // labels          63 octets or less
            if ($element_len > 63) $return_status[]  = ISEMAIL_RFC5322_LABEL_TOOLONG;

            $end_or_die    = false;  // CFWS is OK again now we're at the beginning of an element (although it may be obsolete CFWS)
            $element_len    = 0;
            $element_count++;
            $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  = '';
            $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;

          break;
        // Domain literal
        case ISEMAIL_STRING_OPENSQBRACKET:
          if ($parsedata[ISEMAIL_COMPONENT_DOMAIN] === '') {
            $end_or_die    = true;  // Domain literal must be the only component
            $element_len++;
            $context_stack[]  = $context;
            $context    = ISEMAIL_COMPONENT_LITERAL;
            $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;
            $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  .= $token;
            $parsedata[ISEMAIL_COMPONENT_LITERAL]      = '';
          } else {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_ATEXT;  // Fatal error
          }

          break;
        // Folding White Space
        case ISEMAIL_STRING_CR:
        case ISEMAIL_STRING_SP:
        case ISEMAIL_STRING_HTAB:
          if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;  break;}  // Fatal error

          if ($element_len === 0)
            $return_status[]  = ($element_count === 0) ? ISEMAIL_DEPREC_CFWS_NEAR_AT : ISEMAIL_DEPREC_FWS;
          else {
            $return_status[]  = ISEMAIL_CFWS_FWS;
            $end_or_die  = true;  // We can't start FWS in the middle of an element, so this better be the end
          }

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_FWS;
          $token_prior    = $token;
          break;
        // atext
        default:
          // RFC 5322 allows any atext...
          // http://tools.ietf.org/html/rfc5322#section-3.2.3
          //    atext           =   ALPHA / DIGIT /    ; Printable US-ASCII
          //                        "!" / "#" /        ;  characters not including
          //                        "$" / "%" /        ;  specials.  Used for atoms.
          //                        "&" / "'" /
          //                        "*" / "+" /
          //                        "-" / "/" /
          //                        "=" / "?" /
          //                        "^" / "_" /
          //                        "`" / "{" /
          //                        "|" / "}" /
          //                        "~"

          // But RFC 5321 only allows letter-digit-hyphen to comply with DNS rules (RFCs 1034 & 1123)
          // http://tools.ietf.org/html/rfc5321#section-4.1.2
          //   sub-domain     = Let-dig [Ldh-str]
          //
          //   Let-dig        = ALPHA / DIGIT
          //
          //   Ldh-str        = *( ALPHA / DIGIT / "-" ) Let-dig
          //
          if ($end_or_die) {
            // We have encountered atext where it is no longer valid
            switch ($context_prior) {
            case ISEMAIL_CONTEXT_COMMENT:
            case ISEMAIL_CONTEXT_FWS:
              $return_status[]  = ISEMAIL_ERR_ATEXT_AFTER_CFWS;
              break;
            case ISEMAIL_COMPONENT_LITERAL:
              $return_status[]  = ISEMAIL_ERR_ATEXT_AFTER_DOMLIT;
              break;
            default:
              die ("More atext found where none is allowed, but unrecognised prior context: $context_prior");
            }
          }

          $ord    = ord($token);
          $hyphen_flag  = false;  // Assume this token isn't a hyphen unless we discover it is

          if (($ord < 33) || ($ord > 126) || (!is_bool(strpos(ISEMAIL_STRING_SPECIALS, $token)))) {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_ATEXT;  // Fatal error
          } elseif ($token === ISEMAIL_STRING_HYPHEN) {
            if ($element_len === 0) {
              // Hyphens can't be at the beginning of a subdomain
              $return_status[]  = ISEMAIL_ERR_DOMAINHYPHENSTART;  // Fatal error
            }

            $hyphen_flag = true;
          } elseif (!(($ord > 47 && $ord < 58) || ($ord > 64 && $ord < 91) || ($ord > 96 && $ord < 123))) {
            // Not an RFC 5321 subdomain, but still OK by RFC 5322
            $return_status[]  = ISEMAIL_RFC5322_DOMAIN;
          }

          $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  .= $token;
          $element_len++;
        }

        break;
      //-------------------------------------------------------------
      // Domain literal
      //-------------------------------------------------------------
      case ISEMAIL_COMPONENT_LITERAL:
        // http://tools.ietf.org/html/rfc5322#section-3.4.1
        //   domain-literal  =   [CFWS] "[" *([FWS] dtext) [FWS] "]" [CFWS]
        //
        //   dtext           =   %d33-90 /          ; Printable US-ASCII
        //                       %d94-126 /         ;  characters not including
        //                       obs-dtext          ;  "[", "]", or "\"
        //
        //   obs-dtext       =   obs-NO-WS-CTL / quoted-pair
        switch ($token) {
        // End of domain literal
        case ISEMAIL_STRING_CLOSESQBRACKET:
          if ((int) max($return_status) < ISEMAIL_DEPREC) {
            // Could be a valid RFC 5321 address literal, so let's check

            // http://tools.ietf.org/html/rfc5321#section-4.1.2
            //   address-literal  = "[" ( IPv4-address-literal /
            //                    IPv6-address-literal /
            //                    General-address-literal ) "]"
            //                    ; See Section 4.1.3
            //
            // http://tools.ietf.org/html/rfc5321#section-4.1.3
            //   IPv4-address-literal  = Snum 3("."  Snum)
            //
            //   IPv6-address-literal  = "IPv6:" IPv6-addr
            //
            //   General-address-literal  = Standardized-tag ":" 1*dcontent
            //
            //   Standardized-tag  = Ldh-str
            //                     ; Standardized-tag MUST be specified in a
            //                     ; Standards-Track RFC and registered with IANA
            //
            //   dcontent       = %d33-90 / ; Printable US-ASCII
            //                  %d94-126 ; excl. "[", "\", "]"
            //
            //   Snum           = 1*3DIGIT
            //                  ; representing a decimal integer
            //                  ; value in the range 0 through 255
            //
            //   IPv6-addr      = IPv6-full / IPv6-comp / IPv6v4-full / IPv6v4-comp
            //
            //   IPv6-hex       = 1*4HEXDIG
            //
            //   IPv6-full      = IPv6-hex 7(":" IPv6-hex)
            //
            //   IPv6-comp      = [IPv6-hex *5(":" IPv6-hex)] "::"
            //                  [IPv6-hex *5(":" IPv6-hex)]
            //                  ; The "::" represents at least 2 16-bit groups of
            //                  ; zeros.  No more than 6 groups in addition to the
            //                  ; "::" may be present.
            //
            //   IPv6v4-full    = IPv6-hex 5(":" IPv6-hex) ":" IPv4-address-literal
            //
            //   IPv6v4-comp    = [IPv6-hex *3(":" IPv6-hex)] "::"
            //                  [IPv6-hex *3(":" IPv6-hex) ":"]
            //                  IPv4-address-literal
            //                  ; The "::" represents at least 2 16-bit groups of
            //                  ; zeros.  No more than 4 groups in addition to the
            //                  ; "::" and IPv4-address-literal may be present.
            //
            // is_email() author's note: We can't use ip2long() to validate
            // IPv4 addresses because it accepts abbreviated addresses
            // (xxx.xxx.xxx), expanding the last group to complete the address.
            // filter_var() validates IPv6 address inconsistently (up to PHP 5.3.3
            // at least) -- see http://bugs.php.net/bug.php?id=53236 for example
            $max_groups  = 8;
            $matchesIP  = array();
        /*.mixed.*/  $index    = false;
            $addressliteral  = $parsedata[ISEMAIL_COMPONENT_LITERAL];

            // Extract IPv4 part from the end of the address-literal (if there is one)
            if (preg_match('/\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/', $addressliteral, $matchesIP) > 0) {
              $index = strrpos($addressliteral, $matchesIP[0]);
              if ($index !== 0) $addressliteral = substr($addressliteral, 0, $index) . '0:0'; // Convert IPv4 part to IPv6 format for further testing
            }

            if ($index === 0) {
              // Nothing there except a valid IPv4 address, so...
              $return_status[]  = ISEMAIL_RFC5321_ADDRESSLITERAL;
            } elseif (strncasecmp($addressliteral, ISEMAIL_STRING_IPV6TAG, 5) !== 0) {
              $return_status[]  = ISEMAIL_RFC5322_DOMAINLITERAL;
            } else {
              $IPv6    = substr($addressliteral, 5);
              $matchesIP  = explode(ISEMAIL_STRING_COLON, $IPv6);  // Revision 2.7: Daniel Marschall's new IPv6 testing strategy
              $groupCount  = count($matchesIP);
              $index    = strpos($IPv6,ISEMAIL_STRING_DOUBLECOLON);

              if ($index === false) {
                // We need exactly the right number of groups
                if ($groupCount !== $max_groups)
                  $return_status[]  = ISEMAIL_RFC5322_IPV6_GRPCOUNT;
              } else {
                if ($index !== strrpos($IPv6,ISEMAIL_STRING_DOUBLECOLON))
                  $return_status[]  = ISEMAIL_RFC5322_IPV6_2X2XCOLON;
                else {
                  if ($index === 0 || $index === (strlen($IPv6) - 2)) $max_groups++;  // RFC 4291 allows :: at the start or end of an address with 7 other groups in addition

                  if ($groupCount > $max_groups)
                    $return_status[]  = ISEMAIL_RFC5322_IPV6_MAXGRPS;
                  elseif ($groupCount === $max_groups)
                    $return_status[]  = ISEMAIL_RFC5321_IPV6DEPRECATED;  // Eliding a single "::"
                }
              }

              // Revision 2.7: Daniel Marschall's new IPv6 testing strategy
              if ((substr($IPv6, 0,  1) === ISEMAIL_STRING_COLON) && (substr($IPv6, 1,  1) !== ISEMAIL_STRING_COLON))
                $return_status[]  = ISEMAIL_RFC5322_IPV6_COLONSTRT;  // Address starts with a single colon
              elseif ((substr($IPv6, -1) === ISEMAIL_STRING_COLON) && (substr($IPv6, -2, 1) !== ISEMAIL_STRING_COLON))
                $return_status[]  = ISEMAIL_RFC5322_IPV6_COLONEND;  // Address ends with a single colon
              elseif (count(preg_grep('/^[0-9A-Fa-f]{0,4}$/', $matchesIP, PREG_GREP_INVERT)) !== 0)
                $return_status[]  = ISEMAIL_RFC5322_IPV6_BADCHAR;  // Check for unmatched characters
              else
                $return_status[]  = ISEMAIL_RFC5321_ADDRESSLITERAL;
            }
          } else
            $return_status[]  = ISEMAIL_RFC5322_DOMAINLITERAL;


          $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  .= $token;
          $element_len++;
          $context_prior    = $context;
          $context    = (int) array_pop($context_stack);
          break;
        case ISEMAIL_STRING_BACKSLASH:
          $return_status[]  = ISEMAIL_RFC5322_DOMLIT_OBSDTEXT;
          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_QUOTEDPAIR;
          break;
        // Folding White Space
        case ISEMAIL_STRING_CR:
        case ISEMAIL_STRING_SP:
        case ISEMAIL_STRING_HTAB:
          if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;  break;}  // Fatal error

          $return_status[]  = ISEMAIL_CFWS_FWS;

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_FWS;
          $token_prior    = $token;
          break;
        // dtext
        default:
          // http://tools.ietf.org/html/rfc5322#section-3.4.1
          //   dtext           =   %d33-90 /          ; Printable US-ASCII
          //                       %d94-126 /         ;  characters not including
          //                       obs-dtext          ;  "[", "]", or "\"
          //
          //   obs-dtext       =   obs-NO-WS-CTL / quoted-pair
          //
          //   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
          //                       %d11 /             ;  characters that do not
          //                       %d12 /             ;  include the carriage
          //                       %d14-31 /          ;  return, line feed, and
          //                       %d127              ;  white space characters
          $ord = ord($token);

          // CR, LF, SP & HTAB have already been parsed above
          if (($ord > 127) || ($ord === 0) || ($token === ISEMAIL_STRING_OPENSQBRACKET)) {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_DTEXT;  // Fatal error
            break;
          } elseif (($ord < 33) || ($ord === 127)) {
            $return_status[]  = ISEMAIL_RFC5322_DOMLIT_OBSDTEXT;
          }

          $parsedata[ISEMAIL_COMPONENT_LITERAL]      .= $token;
          $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  .= $token;
          $element_len++;
        }

        break;
      //-------------------------------------------------------------
      // Quoted string
      //-------------------------------------------------------------
      case ISEMAIL_CONTEXT_QUOTEDSTRING:
        // http://tools.ietf.org/html/rfc5322#section-3.2.4
        //   quoted-string   =   [CFWS]
        //                       DQUOTE *([FWS] qcontent) [FWS] DQUOTE
        //                       [CFWS]
        //
        //   qcontent        =   qtext / quoted-pair
        switch ($token) {
        // Quoted pair
        case ISEMAIL_STRING_BACKSLASH:
          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_QUOTEDPAIR;
          break;
        // Folding White Space
        // Inside a quoted string, spaces are allowed as regular characters.
        // It's only FWS if we include HTAB or CRLF
        case ISEMAIL_STRING_CR:
        case ISEMAIL_STRING_HTAB:
          if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;  break;}  // Fatal error

          // http://tools.ietf.org/html/rfc5322#section-3.2.2
          //   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
          //   structured header field are semantically interpreted as a single
          //   space character.

          // http://tools.ietf.org/html/rfc5322#section-3.2.4
          //   the CRLF in any FWS/CFWS that appears within the quoted-string [is]
          //   semantically "invisible" and therefore not part of the quoted-string
          $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= ISEMAIL_STRING_SP;
          $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= ISEMAIL_STRING_SP;
          $element_len++;

          $return_status[]    = ISEMAIL_CFWS_FWS;
          $context_stack[]    = $context;
          $context      = ISEMAIL_CONTEXT_FWS;
          $token_prior      = $token;
          break;
        // End of quoted string
        case ISEMAIL_STRING_DQUOTE:
          $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= $token;
          $element_len++;
          $context_prior      = $context;
          $context      = (int) array_pop($context_stack);
          break;
        // qtext
        default:
          // http://tools.ietf.org/html/rfc5322#section-3.2.4
          //   qtext           =   %d33 /             ; Printable US-ASCII
          //                       %d35-91 /          ;  characters not including
          //                       %d93-126 /         ;  "\" or the quote character
          //                       obs-qtext
          //
          //   obs-qtext       =   obs-NO-WS-CTL
          //
          //   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
          //                       %d11 /             ;  characters that do not
          //                       %d12 /             ;  include the carriage
          //                       %d14-31 /          ;  return, line feed, and
          //                       %d127              ;  white space characters
          $ord = ord($token);

          if (($ord > 127) || ($ord === 0) || ($ord === 10)) {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_QTEXT;  // Fatal error
          } elseif (($ord < 32) || ($ord === 127))
            $return_status[]  = ISEMAIL_DEPREC_QTEXT;

          $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= $token;
          $element_len++;
        }

        // http://tools.ietf.org/html/rfc5322#section-3.4.1
        //   If the
        //   string can be represented as a dot-atom (that is, it contains no
        //   characters other than atext characters or "." surrounded by atext
        //   characters), then the dot-atom form SHOULD be used and the quoted-
        //   string form SHOULD NOT be used.
  // To do
        break;
      //-------------------------------------------------------------
      // Quoted pair
      //-------------------------------------------------------------
      case ISEMAIL_CONTEXT_QUOTEDPAIR:
        // http://tools.ietf.org/html/rfc5322#section-3.2.1
        //   quoted-pair     =   ("\" (VCHAR / WSP)) / obs-qp
        //
        //   VCHAR           =  %d33-126            ; visible (printing) characters
        //   WSP             =  SP / HTAB           ; white space
        //
        //   obs-qp          =   "\" (%d0 / obs-NO-WS-CTL / LF / CR)
        //
        //   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
        //                       %d11 /             ;  characters that do not
        //                       %d12 /             ;  include the carriage
        //                       %d14-31 /          ;  return, line feed, and
        //                       %d127              ;  white space characters
        //
        // i.e. obs-qp       =  "\" (%d0-8, %d10-31 / %d127)
        $ord = ord($token);

        if  ($ord > 127)
            $return_status[]  = ISEMAIL_ERR_EXPECTING_QPAIR;  // Fatal error
        elseif  ((($ord < 31) && ($ord !== 9)) || ($ord === 127))  // SP & HTAB are allowed
            $return_status[]  = ISEMAIL_DEPREC_QP;

        // At this point we know where this qpair occurred so
        // we could check to see if the character actually
        // needed to be quoted at all.
        // http://tools.ietf.org/html/rfc5321#section-4.1.2
        //   the sending system SHOULD transmit the
        //   form that uses the minimum quoting possible.
  // To do: check whether the character needs to be quoted (escaped) in this context
        $context_prior  = $context;
        $context  = (int) array_pop($context_stack);  // End of qpair
        $token    = ISEMAIL_STRING_BACKSLASH . $token;

        switch ($context) {
        case ISEMAIL_CONTEXT_COMMENT:
          break;
        case ISEMAIL_CONTEXT_QUOTEDSTRING:
          $parsedata[ISEMAIL_COMPONENT_LOCALPART]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_LOCALPART][$element_count]  .= $token;
          $element_len  += 2;  // The maximum sizes specified by RFC 5321 are octet counts, so we must include the backslash
          break;
        case ISEMAIL_COMPONENT_LITERAL:
          $parsedata[ISEMAIL_COMPONENT_DOMAIN]      .= $token;
          $atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count]  .= $token;
          $element_len  += 2;  // The maximum sizes specified by RFC 5321 are octet counts, so we must include the backslash
          break;
        default:
          die("Quoted pair logic invoked in an invalid context: $context");
        }

        break;
      //-------------------------------------------------------------
      // Comment
      //-------------------------------------------------------------
      case ISEMAIL_CONTEXT_COMMENT:
        // http://tools.ietf.org/html/rfc5322#section-3.2.2
        //   comment         =   "(" *([FWS] ccontent) [FWS] ")"
        //
        //   ccontent        =   ctext / quoted-pair / comment
        switch ($token) {
        // Nested comment
        case ISEMAIL_STRING_OPENPARENTHESIS:
          // Nested comments are OK
          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_COMMENT;
          break;
        // End of comment
        case ISEMAIL_STRING_CLOSEPARENTHESIS:
          $context_prior    = $context;
          $context    = (int) array_pop($context_stack);

          // http://tools.ietf.org/html/rfc5322#section-3.2.2
          //   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
          //   structured header field are semantically interpreted as a single
          //   space character.
          //
          // is_email() author's note: This *cannot* mean that we must add a
          // space to the address wherever CFWS appears. This would result in
          // any addr-spec that had CFWS outside a quoted string being invalid
          // for RFC 5321.
  //        if (($context === ISEMAIL_COMPONENT_LOCALPART) || ($context === ISEMAIL_COMPONENT_DOMAIN)) {
  //          $parsedata[$context]      .= ISEMAIL_STRING_SP;
  //          $atomlist[$context][$element_count]  .= ISEMAIL_STRING_SP;
  //          $element_len++;
  //        }

          break;
        // Quoted pair
        case ISEMAIL_STRING_BACKSLASH:
          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_QUOTEDPAIR;
          break;
        // Folding White Space
        case ISEMAIL_STRING_CR:
        case ISEMAIL_STRING_SP:
        case ISEMAIL_STRING_HTAB:
          if (($token === ISEMAIL_STRING_CR) && ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))) {$return_status[] = ISEMAIL_ERR_CR_NO_LF;  break;}  // Fatal error

          $return_status[]  = ISEMAIL_CFWS_FWS;

          $context_stack[]  = $context;
          $context    = ISEMAIL_CONTEXT_FWS;
          $token_prior    = $token;
          break;
        // ctext
        default:
          // http://tools.ietf.org/html/rfc5322#section-3.2.3
          //   ctext           =   %d33-39 /          ; Printable US-ASCII
          //                       %d42-91 /          ;  characters not including
          //                       %d93-126 /         ;  "(", ")", or "\"
          //                       obs-ctext
          //
          //   obs-ctext       =   obs-NO-WS-CTL
          //
          //   obs-NO-WS-CTL   =   %d1-8 /            ; US-ASCII control
          //                       %d11 /             ;  characters that do not
          //                       %d12 /             ;  include the carriage
          //                       %d14-31 /          ;  return, line feed, and
          //                       %d127              ;  white space characters
          $ord = ord($token);

          if (($ord > 127) || ($ord === 0) || ($ord === 10)) {
            $return_status[]  = ISEMAIL_ERR_EXPECTING_CTEXT;  // Fatal error
            break;
          } elseif (($ord < 32) || ($ord === 127)) {
            $return_status[]  = ISEMAIL_DEPREC_CTEXT;
          }
        }

        break;
      //-------------------------------------------------------------
      // Folding White Space
      //-------------------------------------------------------------
      case ISEMAIL_CONTEXT_FWS:
        // http://tools.ietf.org/html/rfc5322#section-3.2.2
        //   FWS             =   ([*WSP CRLF] 1*WSP) /  obs-FWS
        //                                          ; Folding white space

        // But note the erratum:
        // http://www.rfc-editor.org/errata_search.php?rfc=5322&eid=1908:
        //   In the obsolete syntax, any amount of folding white space MAY be
        //   inserted where the obs-FWS rule is allowed.  This creates the
        //   possibility of having two consecutive "folds" in a line, and
        //   therefore the possibility that a line which makes up a folded header
        //   field could be composed entirely of white space.
        //
        //   obs-FWS         =   1*([CRLF] WSP)
        if ($token_prior === ISEMAIL_STRING_CR) {
          if ($token === ISEMAIL_STRING_CR) {
            $return_status[]  = ISEMAIL_ERR_FWS_CRLF_X2;  // Fatal error
            break;
          }

          if (isset($crlf_count)) {
            if (++$crlf_count > 1)
              $return_status[]  = ISEMAIL_DEPREC_FWS;  // Multiple folds = obsolete FWS
          } else $crlf_count = 1;
        }

        switch ($token) {
        case ISEMAIL_STRING_CR:
          if ((++$i === $raw_length) || ($email[$i] !== ISEMAIL_STRING_LF))
            $return_status[]  = ISEMAIL_ERR_CR_NO_LF;  // Fatal error

          break;
        case ISEMAIL_STRING_SP:
        case ISEMAIL_STRING_HTAB:
          break;
        default:
          if ($token_prior === ISEMAIL_STRING_CR) {
            $return_status[]  = ISEMAIL_ERR_FWS_CRLF_END;  // Fatal error
            break;
          }

          if (isset($crlf_count)) unset($crlf_count);

          $context_prior          = $context;
          $context          = (int) array_pop($context_stack);  // End of FWS

          // http://tools.ietf.org/html/rfc5322#section-3.2.2
          //   Runs of FWS, comment, or CFWS that occur between lexical tokens in a
          //   structured header field are semantically interpreted as a single
          //   space character.
          //
          // is_email() author's note: This *cannot* mean that we must add a
          // space to the address wherever CFWS appears. This would result in
          // any addr-spec that had CFWS outside a quoted string being invalid
          // for RFC 5321.
  //        if (($context === ISEMAIL_COMPONENT_LOCALPART) || ($context === ISEMAIL_COMPONENT_DOMAIN)) {
  //          $parsedata[$context]      .= ISEMAIL_STRING_SP;
  //          $atomlist[$context][$element_count]  .= ISEMAIL_STRING_SP;
  //          $element_len++;
  //        }

          $i--;  // Look at this token again in the parent context
        }

        $token_prior = $token;
        break;
      //-------------------------------------------------------------
      // A context we aren't expecting
      //-------------------------------------------------------------
      default:
        die("Unknown context: $context");
      }

  //-echo "<td>$context|",(($end_or_die) ? 'true' : 'false'),"|$token|" . max($return_status) . "</td></tr>"; // debug
      if ((int) max($return_status) > ISEMAIL_RFC5322) break;  // No point going on if we've got a fatal error
    }

    // Some simple final tests
    if ((int) max($return_status) < ISEMAIL_RFC5322) {
      if  ($context   === ISEMAIL_CONTEXT_QUOTEDSTRING)  $return_status[]  = ISEMAIL_ERR_UNCLOSEDQUOTEDSTR;  // Fatal error
      elseif  ($context   === ISEMAIL_CONTEXT_QUOTEDPAIR)    $return_status[]  = ISEMAIL_ERR_BACKSLASHEND;    // Fatal error
      elseif  ($context   === ISEMAIL_CONTEXT_COMMENT)    $return_status[]  = ISEMAIL_ERR_UNCLOSEDCOMMENT;    // Fatal error
      elseif  ($context   === ISEMAIL_COMPONENT_LITERAL)    $return_status[]  = ISEMAIL_ERR_UNCLOSEDDOMLIT;    // Fatal error
      elseif  ($token    === ISEMAIL_STRING_CR)      $return_status[]  = ISEMAIL_ERR_FWS_CRLF_END;    // Fatal error
      elseif  ($parsedata[ISEMAIL_COMPONENT_DOMAIN]  === '')    $return_status[]  = ISEMAIL_ERR_NODOMAIN;      // Fatal error
      elseif  ($element_len  === 0)          $return_status[]  = ISEMAIL_ERR_DOT_END;      // Fatal error
      elseif  ($hyphen_flag)            $return_status[]  = ISEMAIL_ERR_DOMAINHYPHENEND;    // Fatal error
      // http://tools.ietf.org/html/rfc5321#section-4.5.3.1.2
      //   The maximum total length of a domain name or number is 255 octets.
      elseif  (strlen($parsedata[ISEMAIL_COMPONENT_DOMAIN]) > 255)
                      $return_status[]  = ISEMAIL_RFC5322_DOMAIN_TOOLONG;
      // http://tools.ietf.org/html/rfc5321#section-4.1.2
      //   Forward-path   = Path
      //
      //   Path           = "<" [ A-d-l ":" ] Mailbox ">"
      //
      // http://tools.ietf.org/html/rfc5321#section-4.5.3.1.3
      //   The maximum total length of a reverse-path or forward-path is 256
      //   octets (including the punctuation and element separators).
      //
      // Thus, even without (obsolete) routing information, the Mailbox can
      // only be 254 characters long. This is confirmed by this verified
      // erratum to RFC 3696:
      //
      // http://www.rfc-editor.org/errata_search.php?rfc=3696&eid=1690
      //   However, there is a restriction in RFC 2821 on the length of an
      //   address in MAIL and RCPT commands of 254 characters.  Since addresses
      //   that do not fit in those fields are not normally useful, the upper
      //   limit on address lengths should normally be considered to be 254.
      elseif  (strlen($parsedata[ISEMAIL_COMPONENT_LOCALPART] . ISEMAIL_STRING_AT . $parsedata[ISEMAIL_COMPONENT_DOMAIN]) > 254)
                      $return_status[]  = ISEMAIL_RFC5322_TOOLONG;
      // http://tools.ietf.org/html/rfc1035#section-2.3.4
      // labels          63 octets or less
      elseif ($element_len > 63)          $return_status[]  = ISEMAIL_RFC5322_LABEL_TOOLONG;
    }

    // Check DNS?
    $dns_checked = false;

    if ($checkDNS && ((int) max($return_status) < ISEMAIL_DNSWARN) && function_exists('dns_get_record')) {
      // http://tools.ietf.org/html/rfc5321#section-2.3.5
      //   Names that can
      //   be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed
      //   in Section 5) are permitted, as are CNAME RRs whose targets can be
      //   resolved, in turn, to MX or address RRs.
      //
      // http://tools.ietf.org/html/rfc5321#section-5.1
      //   The lookup first attempts to locate an MX record associated with the
      //   name.  If a CNAME record is found, the resulting name is processed as
      //   if it were the initial name. ... If an empty list of MXs is returned,
      //   the address is treated as if it was associated with an implicit MX
      //   RR, with a preference of 0, pointing to that host.
      //
      // is_email() author's note: We will regard the existence of a CNAME to be
      // sufficient evidence of the domain's existence. For performance reasons
      // we will not repeat the DNS lookup for the CNAME's target, but we will
      // raise a warning because we didn't immediately find an MX record.
      if ($element_count === 0) $parsedata[ISEMAIL_COMPONENT_DOMAIN] .= '.';    // Checking TLD DNS seems to work only if you explicitly check from the root

      $result = @dns_get_record($parsedata[ISEMAIL_COMPONENT_DOMAIN], DNS_MX);  // Not using checkdnsrr because of a suspected bug in PHP 5.3 (http://bugs.php.net/bug.php?id=51844)

      if ((is_bool($result) && !(bool) $result))
        $return_status[] = ISEMAIL_DNSWARN_NO_RECORD;      // Domain can't be found in DNS
      else {
        if (count($result) === 0) {
          $return_status[]  = ISEMAIL_DNSWARN_NO_MX_RECORD;    // MX-record for domain can't be found
          $result      = @dns_get_record($parsedata[ISEMAIL_COMPONENT_DOMAIN], DNS_A + DNS_CNAME);

          if (count($result) === 0)
            $return_status[] = ISEMAIL_DNSWARN_NO_RECORD;    // No usable records for the domain can be found
        } else $dns_checked = true;
      }
    }

    // Check for TLD addresses
    // -----------------------
    // TLD addresses are specifically allowed in RFC 5321 but they are
    // unusual to say the least. We will allocate a separate
    // status to these addresses on the basis that they are more likely
    // to be typos than genuine addresses (unless we've already
    // established that the domain does have an MX record)
    //
    // http://tools.ietf.org/html/rfc5321#section-2.3.5
    //   In the case
    //   of a top-level domain used by itself in an email address, a single
    //   string is used without any dots.  This makes the requirement,
    //   described in more detail below, that only fully-qualified domain
    //   names appear in SMTP transactions on the public Internet,
    //   particularly important where top-level domains are involved.
    //
    // TLD format
    // ----------
    // The format of TLDs has changed a number of times. The standards
    // used by IANA have been largely ignored by ICANN, leading to
    // confusion over the standards being followed. These are not defined
    // anywhere, except as a general component of a DNS host name (a label).
    // However, this could potentially lead to 123.123.123.123 being a
    // valid DNS name (rather than an IP address) and thereby creating
    // an ambiguity. The most authoritative statement on TLD formats that
    // the author can find is in a (rejected!) erratum to RFC 1123
    // submitted by John Klensin, the author of RFC 5321:
    //
    // http://www.rfc-editor.org/errata_search.php?rfc=1123&eid=1353
    //   However, a valid host name can never have the dotted-decimal
    //   form #.#.#.#, since this change does not permit the highest-level
    //   component label to start with a digit even if it is not all-numeric.
    if (!$dns_checked && ((int) max($return_status) < ISEMAIL_DNSWARN)) {
      if  ($element_count  === 0)  $return_status[]  = ISEMAIL_RFC5321_TLD;

      if  (is_numeric($atomlist[ISEMAIL_COMPONENT_DOMAIN][$element_count][0]))
              $return_status[]  = ISEMAIL_RFC5321_TLDNUMERIC;
    }

    $return_status    = array_unique($return_status);
    $final_status    = (int) max($return_status);

    if (count($return_status) !== 1) array_shift($return_status); // remove redundant ISEMAIL_VALID

    $parsedata['status']  = $return_status;

    if ($final_status < $threshold) $final_status = ISEMAIL_VALID;

    return ($diagnose) ? $final_status : ($final_status < ISEMAIL_THRESHOLD);
  }
}
?>

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