PHP 符合RFC的电子邮件地址验证器
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<?php
/**
* To validate an email address according to RFCs 5321, 5322 and others
*
* Copyright (c) 2008-2010, Dominic Sayers <br>
* Test schema documentation Copyright (c) 2010, 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 2008-2010 Dominic Sayers
* @license http://www.opensource.org/licenses/bsd-license.php BSD License
* @link http://www.dominicsayers.com/isemail
* @version 2.8.3 - Clarified text for ISEMAIL_IPV6BADCHAR and new test #276 added (too many IPv6 groups with an elision)
*/
// 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';
.*/
/**
* Check that an email address conforms to RFCs 5321, 5322 and others
*
* @param string $email The email address to check
* @param boolean $checkDNS If true then a DNS check for A and MX records will be made
* @param mixed $errorlevel If true then return an integer error or warning number rather than true or false
*/
/*.mixed.*/ function is_email ($email, $checkDNS = false, $errorlevel = false) {
// 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)
// $errorlevel Behaviour
// --------------- ---------------------------------------------------------------------------
// E_ERROR Return validation failures only. For technically valid addresses return
// ISEMAIL_VALID
// E_WARNING Return warnings for unlikely but technically valid addresses. This includes
// addresses at TLDs (e.g. johndoe@com), addresses with FWS and comments,
// addresses that are quoted and addresses that contain no alphabetic or
// numeric characters.
// true Same as E_ERROR
// false Return true for valid addresses, false for invalid ones. No warnings.
//
// Errors can be distinguished from warnings if ($return_value > ISEMAIL_ERROR)
// version 2.0: Enhance $diagnose parameter to $errorlevel
// revision 2.5: some syntax changes to make it more PHPLint-friendly. Should be functionally identical.
if (!defined('ISEMAIL_VALID')) {
// No errors
define('ISEMAIL_VALID' , 0);
// Warnings (valid address but unlikely in the real world)
define('ISEMAIL_WARNING' , 64);
define('ISEMAIL_TLD' , 65);
define('ISEMAIL_TLDNUMERIC' , 66);
define('ISEMAIL_QUOTEDSTRING' , 67);
define('ISEMAIL_COMMENTS' , 68);
define('ISEMAIL_FWS' , 69);
define('ISEMAIL_ADDRESSLITERAL' , 70);
define('ISEMAIL_UNLIKELYINITIAL' , 71);
define('ISEMAIL_SINGLEGROUPELISION' , 72);
define('ISEMAIL_DOMAINNOTFOUND' , 73);
define('ISEMAIL_MXNOTFOUND' , 74);
// Errors (invalid address)
define('ISEMAIL_ERROR' , 128);
define('ISEMAIL_TOOLONG' , 129);
define('ISEMAIL_NOAT' , 130);
define('ISEMAIL_NOLOCALPART' , 131);
define('ISEMAIL_NODOMAIN' , 132);
define('ISEMAIL_ZEROLENGTHELEMENT' , 133);
define('ISEMAIL_BADCOMMENT_START' , 134);
define('ISEMAIL_BADCOMMENT_END' , 135);
define('ISEMAIL_UNESCAPEDDELIM' , 136);
define('ISEMAIL_EMPTYELEMENT' , 137);
define('ISEMAIL_UNESCAPEDSPECIAL' , 138);
define('ISEMAIL_LOCALTOOLONG' , 139);
// define('ISEMAIL_IPV4BADPREFIX' , 140);
define('ISEMAIL_IPV6BADPREFIXMIXED' , 141);
define('ISEMAIL_IPV6BADPREFIX' , 142);
define('ISEMAIL_IPV6GROUPCOUNT' , 143);
define('ISEMAIL_IPV6DOUBLEDOUBLECOLON' , 144);
define('ISEMAIL_IPV6BADCHAR' , 145);
define('ISEMAIL_IPV6TOOMANYGROUPS' , 146);
define('ISEMAIL_DOMAINEMPTYELEMENT' , 147);
define('ISEMAIL_DOMAINELEMENTTOOLONG' , 148);
define('ISEMAIL_DOMAINBADCHAR' , 149);
define('ISEMAIL_DOMAINTOOLONG' , 150);
define('ISEMAIL_IPV6SINGLECOLONSTART' , 151);
define('ISEMAIL_IPV6SINGLECOLONEND' , 152);
// Unexpected errors
// define('ISEMAIL_BADPARAMETER' , 190);
// define('ISEMAIL_NOTDEFINED' , 191);
// revision 2.1: Redefined unexpected error constants so they don't clash with the ISEMAIL_WARNING bit
// revision 2.5: Undefined unused constants
}
if (is_bool($errorlevel)) {
if ((bool) $errorlevel) {
$diagnose = true;
$warn = false;
} else {
$diagnose = false;
$warn = false;
}
} else {
switch ((int) $errorlevel) {
case E_WARNING:
$diagnose = true;
$warn = true;
break;
case E_ERROR:
$diagnose = true;
$warn = false;
break;
default:
$diagnose = false;
$warn = false;
}
}
if ($diagnose) /*.mixed.*/ $return_status = ISEMAIL_VALID; else $return_status = true;
// version 2.0: Enhance $diagnose parameter to $errorlevel
// the upper limit on address lengths should normally be considered to be 254
// (http://www.rfc-editor.org/errata_search.php?rfc=3696)
// NB My erratum has now been verified by the IETF so the correct answer is 254
//
// The maximum total length of a reverse-path or forward-path is 256
// characters (including the punctuation and element separators)
// (http://tools.ietf.org/html/rfc5321#section-4.5.3.1.3)
// NB There is a mandatory 2-character wrapper round the actual address
$emailLength = strlen($email);
// revision 1.17: Max length reduced to 254 (see above)
if ($emailLength > 254) if ($diagnose) return ISEMAIL_TOOLONG; else return false; // Too long
// Contemporary email addresses consist of a "local part" separated from
// a "domain part" (a fully-qualified domain name) by an at-sign ("@").
// (http://tools.ietf.org/html/rfc3696#section-3)
$atIndex = strrpos($email,'@');
if ($atIndex === false) if ($diagnose) return ISEMAIL_NOAT; else return false; // No at-sign
if ($atIndex === 0) if ($diagnose) return ISEMAIL_NOLOCALPART; else return false; // No local part
if ($atIndex === $emailLength - 1) if ($diagnose) return ISEMAIL_NODOMAIN; else return false; // No domain part
// revision 1.14: Length test bug suggested by Andrew Campbell of Gloucester, MA
// Sanitize comments
// - remove nested comments, quotes and dots in comments
// - remove parentheses and dots from quoted strings
$braceDepth = 0;
$inQuote = false;
$escapeThisChar = false;
for ($i = 0; $i < $emailLength; ++$i) {
$char = $email[$i];
$replaceChar = false;
if ($char === '\\') $escapeThisChar = !$escapeThisChar; // Escape the next character?
else {
switch ($char) {
case '(':
if ($escapeThisChar) $replaceChar = true;
else if ($inQuote) $replaceChar = true;
else if ($braceDepth++ > 0) $replaceChar = true; // Increment brace depth
break;
case ')':
if ($escapeThisChar) $replaceChar = true;
else if ($inQuote) $replaceChar = true;
else {
if (--$braceDepth > 0) $replaceChar = true; // Decrement brace depth
if ($braceDepth < 0) $braceDepth = 0;
}
break;
case '"':
if ($escapeThisChar) $replaceChar = true;
else if ($braceDepth === 0) $inQuote = !$inQuote; // Are we inside a quoted string?
else $replaceChar = true;
break;
case '.':
if ($escapeThisChar) $replaceChar = true; // Dots don't help us either
else if ($braceDepth > 0) $replaceChar = true;
break;
default:
}
$escapeThisChar = false;
// if ($replaceChar) $email[$i] = 'x'; // Replace the offending character with something harmless
// revision 1.12: Line above replaced because PHPLint doesn't like that syntax
if ($replaceChar) $email = (string) substr_replace($email, 'x', $i, 1); // Replace the offending character with something harmless
}
}
$localPart = substr($email, 0, $atIndex);
$domain = substr($email, $atIndex + 1);
$FWS = "(?:(?:(?:[ \\t]*(?:\\r\\n))?[ \\t]+)|(?:[ \\t]+(?:(?:\\r\\n)[ \\t]+)*))"; // Folding white space
$dotArray = /*. (array[]) .*/ array();
// Let's check the local part for RFC compliance...
//
// local-part = dot-atom / quoted-string / obs-local-part
// obs-local-part = word *("." word)
// (http://tools.ietf.org/html/rfc5322#section-3.4.1)
//
// Problem: need to distinguish between "first.last" and "first"."last"
// (i.e. one element or two). And I suck at regexes.
$dotArray = preg_split('/\\.(?=(?:[^\\"]*\\"[^\\"]*\\")*(?![^\\"]*\\"))/m', $localPart);
$partLength = 0;
foreach ($dotArray as $arrayMember) {
$element = (string) $arrayMember;
// Remove any leading or trailing FWS
$new_element = preg_replace("/^$FWS|$FWS\$/", '', $element);
if ($warn && ($element !== $new_element)) $return_status = ISEMAIL_FWS; // FWS is unlikely in the real world
$element = $new_element;
// version 2.3: Warning condition added
$elementLength = strlen($element);
if ($elementLength === 0) if ($diagnose) return ISEMAIL_ZEROLENGTHELEMENT; else return false; // Can't have empty element (consecutive dots or dots at the start or end)
// revision 1.15: Speed up the test and get rid of "unitialized string offset" notices from PHP
// We need to remove any valid comments (i.e. those at the start or end of the element)
if ($element[0] === '(') {
if ($warn) $return_status = ISEMAIL_COMMENTS; // Comments are unlikely in the real world
// version 2.0: Warning condition added
$indexBrace = strpos($element, ')');
if ($indexBrace !== false) {
if (preg_match('/(?<!\\\\)[\\(\\)]/', substr($element, 1, $indexBrace - 1)) > 0)
if ($diagnose) return ISEMAIL_BADCOMMENT_START; else return false; // Illegal characters in comment
$element = substr($element, $indexBrace + 1, $elementLength - $indexBrace - 1);
$elementLength = strlen($element);
}
}
if ($element[$elementLength - 1] === ')') {
if ($warn) $return_status = ISEMAIL_COMMENTS; // Comments are unlikely in the real world
// version 2.0: Warning condition added
$indexBrace = strrpos($element, '(');
if ($indexBrace !== false) {
if (preg_match('/(?<!\\\\)(?:[\\(\\)])/', substr($element, $indexBrace + 1, $elementLength - $indexBrace - 2)) > 0)
if ($diagnose) return ISEMAIL_BADCOMMENT_END; else return false; // Illegal characters in comment
$element = substr($element, 0, $indexBrace);
$elementLength = strlen($element);
}
}
// Remove any remaining leading or trailing FWS around the element (having removed any comments)
$new_element = preg_replace("/^$FWS|$FWS\$/", '', $element);
if ($warn && ($element !== $new_element)) $return_status = ISEMAIL_FWS; // FWS is unlikely in the real world
$element = $new_element;
// version 2.0: Warning condition added
// What's left counts towards the maximum length for this part
if ($partLength > 0) $partLength++; // for the dot
$partLength += strlen($element);
// Each dot-delimited component can be an atom or a quoted string
// (because of the obs-local-part provision)
if (preg_match('/^"(?:.)*"$/s', $element) > 0) {
// Quoted-string tests:
if ($warn) $return_status = ISEMAIL_QUOTEDSTRING; // Quoted string is unlikely in the real world
// version 2.0: Warning condition added
// Remove any FWS
$element = preg_replace("/(?<!\\\\)$FWS/", '', $element); // A warning condition, but we've already raised ISEMAIL_QUOTEDSTRING
// My regex skillz aren't up to distinguishing between \" \\" \\\" \\\\" etc.
// So remove all \\ from the string first...
$element = preg_replace('/\\\\\\\\/', ' ', $element);
if (preg_match('/(?<!\\\\|^)["\\r\\n\\x00](?!$)|\\\\"$|""/', $element) > 0) if ($diagnose) return ISEMAIL_UNESCAPEDDELIM; else return false; // ", CR, LF and NUL must be escaped
// version 2.0: allow ""@example.com because it's technically valid
} else {
// Unquoted string tests:
//
// Period (".") may...appear, but may not be used to start or end the
// local part, nor may two or more consecutive periods appear.
// (http://tools.ietf.org/html/rfc3696#section-3)
//
// A zero-length element implies a period at the beginning or end of the
// local part, or two periods together. Either way it's not allowed.
if ($element === '') if ($diagnose) return ISEMAIL_EMPTYELEMENT; else return false; // Dots in wrong place
// Any ASCII graphic (printing) character other than the
// at-sign ("@"), backslash, double quote, comma, or square brackets may
// appear without quoting. If any of that list of excluded characters
// are to appear, they must be quoted
// (http://tools.ietf.org/html/rfc3696#section-3)
//
// Any excluded characters? i.e. 0x00-0x20, (, ), <, >, [, ], :, ;, @, \, comma, period, "
if (preg_match('/[\\x00-\\x20\\(\\)<>\\[\\]:;@\\\\,\\."]/', $element) > 0) if ($diagnose) return ISEMAIL_UNESCAPEDSPECIAL; else return false; // These characters must be in a quoted string
if ($warn && (preg_match('/^\\w+/', $element) === 0)) $return_status = ISEMAIL_UNLIKELYINITIAL; // First character is an odd one
}
}
if ($partLength > 64) if ($diagnose) return ISEMAIL_LOCALTOOLONG; else return false; // Local part must be 64 characters or less
// Now let's check the domain part...
// The domain name can also be replaced by an IP address in square brackets
// (http://tools.ietf.org/html/rfc3696#section-3)
// (http://tools.ietf.org/html/rfc5321#section-4.1.3)
// (http://tools.ietf.org/html/rfc4291#section-2.2)
if (preg_match('/^\\[(.)+]$/', $domain) === 1) {
// It's an address-literal
if ($warn) $return_status = ISEMAIL_ADDRESSLITERAL; // Quoted string is unlikely in the real world
// version 2.0: Warning condition added
$addressLiteral = substr($domain, 1, strlen($domain) - 2);
$groupMax = 8;
// revision 2.1: new IPv6 testing strategy
$matchesIP = array();
$colon = ':'; // Revision 2.7: Daniel Marschall's new IPv6 testing strategy
$double_colon = '::';
// Extract IPv4 part from the end of the address-literal (if there is one)
if (preg_match('/\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/', $addressLiteral, $matchesIP) > 0) {
$index = strrpos($addressLiteral, $matchesIP[0]);
if ($index === 0) {
// Nothing there except a valid IPv4 address, so...
if ($diagnose) return $return_status; else return true;
// version 2.0: return warning if one is set
} else {
//- // Assume it's an attempt at a mixed address (IPv6 + IPv4)
//- if ($addressLiteral[$index - 1] !== $colon) if ($diagnose) return ISEMAIL_IPV4BADPREFIX; else return false; // Character preceding IPv4 address must be ':'
// revision 2.1: new IPv6 testing strategy
if (substr($addressLiteral, 0, 5) !== 'IPv6:') if ($diagnose) return ISEMAIL_IPV6BADPREFIXMIXED; else return false; // RFC5321 section 4.1.3
//-
//- $IPv6 = substr($addressLiteral, 5, ($index === 7) ? 2 : $index - 6);
//- $groupMax = 6;
// revision 2.1: new IPv6 testing strategy
$IPv6 = substr($addressLiteral, 5, $index - 5) . '0000:0000'; // Convert IPv4 part to IPv6 format
}
} else {
// It must be an attempt at pure IPv6
if (substr($addressLiteral, 0, 5) !== 'IPv6:') if ($diagnose) return ISEMAIL_IPV6BADPREFIX; else return false; // RFC5321 section 4.1.3
$IPv6 = substr($addressLiteral, 5);
//- $groupMax = 8;
// revision 2.1: new IPv6 testing strategy
}
$matchesIP = explode($colon, $IPv6); // Revision 2.7: Daniel Marschall's new IPv6 testing strategy
$groupCount = count($matchesIP);
$index = strpos($IPv6,$double_colon);
if ($index === false) {
// We need exactly the right number of groups
if ($groupCount !== $groupMax) if ($diagnose) return ISEMAIL_IPV6GROUPCOUNT; else return false; // RFC5321 section 4.1.3
} else {
if ($index !== strrpos($IPv6,$double_colon)) if ($diagnose) return ISEMAIL_IPV6DOUBLEDOUBLECOLON; else return false; // More than one '::'
if ($index === 0 || $index === (strlen($IPv6) - 2)) $groupMax++; // RFC 4291 allows :: at the start or end of an address with 7 other groups in addition
if ($groupCount > $groupMax) if ($diagnose) return ISEMAIL_IPV6TOOMANYGROUPS; else return false; // Too many IPv6 groups in address
if ($groupCount === $groupMax) $return_status = ISEMAIL_SINGLEGROUPELISION; // Eliding a single group with :: is deprecated by RFCs 5321 & 5952
}
// Check for single : at start and end of address
// Revision 2.7: Daniel Marschall's new IPv6 testing strategy
if ((substr($IPv6, 0, 1) === $colon) && (substr($IPv6, 1, 1) !== $colon)) if ($diagnose) return ISEMAIL_IPV6SINGLECOLONSTART; else return false; // Address starts with a single colon
if ((substr($IPv6, -1) === $colon) && (substr($IPv6, -2, 1) !== $colon)) if ($diagnose) return ISEMAIL_IPV6SINGLECOLONEND; else return false; // Address ends with a single colon
// Check for unmatched characters
if (count(preg_grep('/^[0-9A-Fa-f]{0,4}$/', $matchesIP, PREG_GREP_INVERT)) !== 0) if ($diagnose) return ISEMAIL_IPV6BADCHAR ; else return false; // Illegal characters in address
// It's a valid IPv6 address, so...
if ($diagnose) return $return_status; else return true;
// revision 2.1: bug fix: now correctly return warning status
} else {
// It's a domain name...
// The syntax of a legal Internet host name was specified in RFC-952
// One aspect of host name syntax is hereby changed: the
// restriction on the first character is relaxed to allow either a
// letter or a digit.
// (http://tools.ietf.org/html/rfc1123#section-2.1)
//
// NB RFC 1123 updates RFC 1035, but this is not currently apparent from reading RFC 1035.
//
// Most common applications, including email and the Web, will generally not
// permit...escaped strings
// (http://tools.ietf.org/html/rfc3696#section-2)
//
// the better strategy has now become to make the "at least one period" test,
// to verify LDH conformance (including verification that the apparent TLD name
// is not all-numeric)
// (http://tools.ietf.org/html/rfc3696#section-2)
//
// Characters outside the set of alphabetic characters, digits, and hyphen MUST NOT appear in domain name
// labels for SMTP clients or servers
// (http://tools.ietf.org/html/rfc5321#section-4.1.2)
//
// RFC5321 precludes the use of a trailing dot in a domain name for SMTP purposes
// (http://tools.ietf.org/html/rfc5321#section-4.1.2)
$dotArray = preg_split('/\\.(?=(?:[^\\"]*\\"[^\\"]*\\")*(?![^\\"]*\\"))/m', $domain);
$partLength = 0;
$element = ''; // Since we use $element after the foreach loop let's make sure it has a value
// revision 1.13: Line above added because PHPLint now checks for Definitely Assigned Variables
if ($warn && (count($dotArray) === 1)) $return_status = ISEMAIL_TLD; // The mail host probably isn't a TLD
// version 2.0: downgraded to a warning
foreach ($dotArray as $arrayMember) {
$element = (string) $arrayMember;
// Remove any leading or trailing FWS
$new_element = preg_replace("/^$FWS|$FWS\$/", '', $element);
if ($warn && ($element !== $new_element)) $return_status = ISEMAIL_FWS; // FWS is unlikely in the real world
$element = $new_element;
// version 2.0: Warning condition added
$elementLength = strlen($element);
// Each dot-delimited component must be of type atext
// A zero-length element implies a period at the beginning or end of the
// local part, or two periods together. Either way it's not allowed.
if ($elementLength === 0) if ($diagnose) return ISEMAIL_DOMAINEMPTYELEMENT; else return false; // Dots in wrong place
// revision 1.15: Speed up the test and get rid of "unitialized string offset" notices from PHP
// Then we need to remove all valid comments (i.e. those at the start or end of the element
if ($element[0] === '(') {
if ($warn) $return_status = ISEMAIL_COMMENTS; // Comments are unlikely in the real world
// version 2.0: Warning condition added
$indexBrace = strpos($element, ')');
if ($indexBrace !== false) {
if (preg_match('/(?<!\\\\)[\\(\\)]/', substr($element, 1, $indexBrace - 1)) > 0)
if ($diagnose) return ISEMAIL_BADCOMMENT_START; else return false; // Illegal characters in comment
// revision 1.17: Fixed name of constant (also spotted by turboflash - thanks!)
$element = substr($element, $indexBrace + 1, $elementLength - $indexBrace - 1);
$elementLength = strlen($element);
}
}
if ($element[$elementLength - 1] === ')') {
if ($warn) $return_status = ISEMAIL_COMMENTS; // Comments are unlikely in the real world
// version 2.0: Warning condition added
$indexBrace = strrpos($element, '(');
if ($indexBrace !== false) {
if (preg_match('/(?<!\\\\)(?:[\\(\\)])/', substr($element, $indexBrace + 1, $elementLength - $indexBrace - 2)) > 0)
if ($diagnose) return ISEMAIL_BADCOMMENT_END; else return false; // Illegal characters in comment
// revision 1.17: Fixed name of constant (also spotted by turboflash - thanks!)
$element = substr($element, 0, $indexBrace);
$elementLength = strlen($element);
}
}
// Remove any leading or trailing FWS around the element (inside any comments)
$new_element = preg_replace("/^$FWS|$FWS\$/", '', $element);
if ($warn && ($element !== $new_element)) $return_status = ISEMAIL_FWS; // FWS is unlikely in the real world
$element = $new_element;
// version 2.0: Warning condition added
// What's left counts towards the maximum length for this part
if ($partLength > 0) $partLength++; // for the dot
$partLength += strlen($element);
// The DNS defines domain name syntax very generally -- a
// string of labels each containing up to 63 8-bit octets,
// separated by dots, and with a maximum total of 255
// octets.
// (http://tools.ietf.org/html/rfc1123#section-6.1.3.5)
if ($elementLength > 63) if ($diagnose) return ISEMAIL_DOMAINELEMENTTOOLONG; else return false; // Label must be 63 characters or less
// Any ASCII graphic (printing) character other than the
// at-sign ("@"), backslash, double quote, comma, or square brackets may
// appear without quoting. If any of that list of excluded characters
// are to appear, they must be quoted
// (http://tools.ietf.org/html/rfc3696#section-3)
//
// If the hyphen is used, it is not permitted to appear at
// either the beginning or end of a label.
// (http://tools.ietf.org/html/rfc3696#section-2)
//
// Any excluded characters? i.e. 0x00-0x20, (, ), <, >, [, ], :, ;, @, \, comma, period, "
if (preg_match('/[\\x00-\\x20\\(\\)<>\\[\\]:;@\\\\,\\."]|^-|-$/', $element) > 0) if ($diagnose) return ISEMAIL_DOMAINBADCHAR; else return false; // Illegal character in domain name
}
if ($partLength > 255) if ($diagnose) return ISEMAIL_DOMAINTOOLONG; else return false; // Domain part must be 255 characters or less (http://tools.ietf.org/html/rfc1123#section-6.1.3.5)
if ($warn && (preg_match('/^[0-9]+$/', $element) > 0)) $return_status = ISEMAIL_TLDNUMERIC; // TLD probably isn't all-numeric (http://www.apps.ietf.org/rfc/rfc3696.html#sec-2)
// version 2.0: Downgraded to a warning
// Check DNS?
if ($diagnose && ($return_status === ISEMAIL_VALID) && $checkDNS && function_exists('checkdnsrr')) {
if (!(checkdnsrr($domain, 'A'))) $return_status = ISEMAIL_DOMAINNOTFOUND; // 'A' record for domain can't be found
if (!(checkdnsrr($domain, 'MX'))) $return_status = ISEMAIL_MXNOTFOUND; // 'MX' record for domain can't be found
}
}
// Eliminate all other factors, and the one which remains must be the truth.
// (Sherlock Holmes, The Sign of Four)
if ($diagnose) return $return_status; else return true;
// version 2.0: return warning if one is set
}
$email = 'dominic@sayers.cc';
echo "Testing $email<br/>";
echo "$email is " . ((is_email($email)) ? '' : 'not ') . 'a valid email address';
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