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A PHP function that validates all parts of a given email address, according to RFCs 1123, 2396, 3696, 4291, 4343, 5321 & 5322. I’ve released it under a license that allows you to use it royalty-free in commercial or non-commercial work, subject to a few conditions. It’s almost certainly the first email address validator that correctly lets you put an IPv6 address in for the domain part…
<?
/*
Copyright 2009 Dominic Sayers
(dominic_sayers@hotmail.com)
(http://www.dominicsayers.com)
This source file is subject to the Common Public Attribution License Version 1.0 (CPAL) license.
The license terms are available through the world-wide-web at http://www.opensource.org/licenses/cpal_1.0
*/
function is_email ($email, $checkDNS = false) {
// Check that $email is a valid address
// (http://tools.ietf.org/html/rfc3696)
// (http://tools.ietf.org/html/rfc5322#section-3.4.1)
// (http://tools.ietf.org/html/rfc5321#section-4.1.3)
// (http://tools.ietf.org/html/rfc4291#section-2.2)
// (http://tools.ietf.org/html/rfc1123#section-2.1)
// 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)
$index = strrpos($email,'@');
if ($index === false) return false; // No at-sign
if ($index === 0) return false; // No local part
if ($index > 64) return false; // Local part too long
$localPart = substr($email, 0, $index);
$domain = substr($email, $index + 1);
$domainLength = strlen($domain);
if ($domainLength === 0) return false; // No domain part
if ($domainLength > 255) return false; // Domain part too long
// Let's check the local part for RFC compliance...
//
// 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)
if (preg_match('/^\\.|\\.\\.|\\.$/', $localPart) > 0) return false; // Dots in wrong place
// Any ASCII graphic (printing) character other than the
// at-sign ("@"), backslash, double quote, comma, or square brackets may
// appear without quoting. If any of that list of excluded characters
// are to appear, they must be quoted
// (http://tools.ietf.org/html/rfc3696#section-3)
if (preg_match('/^"(?:.)*"$/', $localPart) > 0) {
// Local part is a quoted string
if (preg_match('/(?:.)+[^\\\\]"(?:.)+/', $localPart) > 0) return false; // Unescaped quote character inside quoted string
} else {
if (preg_match('/[ @\\[\\]\\\\",]/', $localPart) > 0)
// Check all excluded characters are escaped
$stripped = preg_replace('/\\\\[ @\\[\\]\\\\",]/', '', $localPart);
if (preg_match('/[ @\\[\\]\\\\",]/', $stripped) > 0) return false; // Unquoted excluded characters
}
// Now let's check the domain part...
// The domain name can also be replaced by an IP address in square brackets
// (http://tools.ietf.org/html/rfc3696#section-3)
// (http://tools.ietf.org/html/rfc5321#section-4.1.3)
// (http://tools.ietf.org/html/rfc4291#section-2.2)
if (preg_match('/^\\[(.)+]$/', $domain) === 1) {
// It's an address-literal
$addressLiteral = substr($domain, 1, $domainLength - 2);
$matchesIP = array();
// Extract IPv4 part from the end of the address-literal (if there is one)
if (preg_match('/\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/', $addressLiteral, $matchesIP) > 0) {
$index = strrpos($addressLiteral, $matchesIP[0]);
if ($index === 0) {
// Nothing there except a valid IPv4 address, so...
return true;
} else {
// Assume it's an attempt at a mixed address (IPv6 + IPv4)
if ($addressLiteral[$index - 1] !== ':') return false; // Character preceding IPv4 address must be ':'
if (substr($addressLiteral, 0, 5) !== 'IPv6:') return false; // RFC5321 section 4.1.3
$IPv6 = substr($addressLiteral, 5, ($index ===7) ? 2 : $index - 6);
$groupMax = 6;
}
} else {
// It must be an attempt at pure IPv6
if (substr($addressLiteral, 0, 5) !== 'IPv6:') return false; // RFC5321 section 4.1.3
$IPv6 = substr($addressLiteral, 5);
$groupMax = 8;
}
$groupCount = preg_match_all('/^[0-9a-fA-F]{0,4}|\\:[0-9a-fA-F]{0,4}|(.)/', $IPv6, $matchesIP);
$index = strpos($IPv6,'::');
if ($index === false) {
// We need exactly the right number of groups
if ($groupCount !== $groupMax) return false; // RFC5321 section 4.1.3
} else {
if ($index !== strrpos($IPv6,'::')) return false; // More than one '::'
$groupMax = ($index === 0 || $index === (strlen($IPv6) - 2)) ? $groupMax : $groupMax - 1;
if ($groupCount > $groupMax) return false; // Too many IPv6 groups in address
}
// Check for unmatched characters
array_multisort($matchesIP[1], SORT_DESC);
if ($matchesIP[1][0] !== '') return false; // Illegal characters in address
// It's a valid IPv6 address, so...
return true;
} 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)
//
// 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)
$matches = array();
$groupCount = preg_match_all('/(?:[0-9a-zA-Z][0-9a-zA-Z-]{0,61}[0-9a-zA-Z]|[a-zA-Z])(?:\\.|$)|(.)/', $domain, $matches);
$level = count($matches[0]);
if ($level == 1) return false; // Mail host can't be a TLD
$TLD = $matches[0][$level - 1];
if (substr($TLD, strlen($TLD) - 1, 1) === '.') return false; // TLD can't end in a dot
if (preg_match('/^[0-9]+$/', $TLD) > 0) return false; // TLD can't be all-numeric
// Check for unmatched characters
array_multisort($matches[1], SORT_DESC);
if ($matches[1][0] !== '') return false; // Illegal characters in domain, or label longer than 63 characters
// Check DNS?
if ($checkDNS && function_exists('checkdnsrr')) {
if (!(checkdnsrr($domain, 'A') || checkdnsrr($domain, 'MX'))) {
return false; // Domain doesn't actually exist
}
}
// Eliminate all other factors, and the one which remains must be the truth.
// (Sherlock Holmes, The Sign of Four)
return true;
}
}
function unitTest ($email, $reason = '') {
$expected = ($reason === '') ? true : false;
$valid = is_email($email);
$not = ($valid) ? '' : ' not';
$unexpected = ($valid !== $expected) ? ' <b>This was unexpected!</b>' : '';
$reason = ($reason === '') ? "" : " Reason: $reason";
return "The address <i>$email</i> is$not valid.$unexpected$reason<br />\n";
}
// Email validator test cases (Dominic Sayers, January 2009)
// Valid addresses
echo unitTest('first.last@example.com');
echo unitTest('1234567890123456789012345678901234567890123456789012345678901234@example.com');
echo unitTest('"first last"@example.com');
echo unitTest('"first\\"last"@example.com'); // Not totally sure whether this is valid or not
echo unitTest('first\\@last@example.com');
echo unitTest('"first@last"@example.com');
echo unitTest('first\\\\last@example.com'); // Note that \ is escaped even in single-quote strings, so this is testing "first\\last"@example.com
echo unitTest('first.last@x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x2345');
echo unitTest('first.last@[12.34.56.78]');
echo unitTest('first.last@[IPv6:::12.34.56.78]');
echo unitTest('first.last@[IPv6:1111:2222:3333::4444:12.34.56.78]');
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666:12.34.56.78]');
echo unitTest('first.last@[IPv6:::1111:2222:3333:4444:5555:6666]');
echo unitTest('first.last@[IPv6:1111:2222:3333::4444:5555:6666]');
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666::]');
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:8888]');
echo unitTest('first.last@x23456789012345678901234567890123456789012345678901234567890123.example.com');
echo unitTest('first.last@1xample.com');
echo unitTest('first.last@123.example.com');
// Invalid addresses
echo unitTest('first.last', "No @");
echo unitTest('@example.com', "No local part");
echo unitTest('12345678901234567890123456789012345678901234567890123456789012345@example.com', "Local part more than 64 characters");
echo unitTest('.first.last@example.com', "Local part starts with a dot");
echo unitTest('first.last.@example.com', "Local part ends with a dot");
echo unitTest('first..last@example.com', "Local part has consecutive dots");
echo unitTest('"first"last"@example.com', "Local part contains unescaped excluded characters");
echo unitTest('first\\\\@last@example.com', "Local part contains unescaped excluded characters");
echo unitTest('first.last@', "No domain");
echo unitTest('first.last@x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456789.x23456', "Domain exceeds 255 chars");
echo unitTest('first.last@[.12.34.56.78]', "Only char that can precede IPv4 address is ':'");
echo unitTest('first.last@[12.34.56.789]', "Can't be interpreted as IPv4 so IPv6 tag is missing");
echo unitTest('first.last@[::12.34.56.78]', "IPv6 tag is missing");
echo unitTest('first.last@[IPv5:::12.34.56.78]', "IPv6 tag is wrong");
echo unitTest('first.last@[IPv6:1111:2222:3333::4444:5555:12.34.56.78]', "Too many IPv6 groups (4 max)");
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:12.34.56.78]', "Not enough IPv6 groups");
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:12.34.56.78]', "Too many IPv6 groups (6 max)");
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777]', "Not enough IPv6 groups");
echo unitTest('first.last@[IPv6:1111:2222:3333:4444:5555:6666:7777:8888:9999]', "Too many IPv6 groups (8 max)");
echo unitTest('first.last@[IPv6:1111:2222::3333::4444:5555:6666]', "Too many '::' (can be none or one)");
echo unitTest('first.last@[IPv6:1111:2222:3333::4444:5555:6666:7777]', "Too many IPv6 groups (6 max)");
echo unitTest('first.last@[IPv6:1111:2222:333x::4444:5555]', "x is not valid in an IPv6 address");
echo unitTest('first.last@[IPv6:1111:2222:33333::4444:5555]', "33333 is not a valid group in an IPv6 address");
echo unitTest('first.last@example.123', "TLD can't be all digits");
echo unitTest('first.last@com', "Mail host must be second- or lower level");
echo unitTest('first.last@-xample.com', "Label can't begin with a hyphen");
echo unitTest('first.last@exampl-.com', "Label can't end with a hyphen");
echo unitTest('first.last@x234567890123456789012345678901234567890123456789012345678901234.example.com', "Label can't be longer than 63 octets");
// Test cases from RFC3696 (February 2004, http://tools.ietf.org/html/rfc3696#section-3)
echo unitTest('Abc\\@def@example.com');
echo unitTest('Fred\\ Bloggs@example.com');
echo unitTest('Joe.\\\\Blow@example.com');
echo unitTest('"Abc@def"@example.com');
echo unitTest('"Fred Bloggs"@example.com');
echo unitTest('user+mailbox@example.com');
echo unitTest('customer/department=shipping@example.com');
echo unitTest('$A12345@example.com');
echo unitTest('!def!xyz%abc@example.com');
echo unitTest('_somename@example.com');
// Test cases from Doug Lovell (LinuxJournal, June 2007, http://www.linuxjournal.com/article/9585)
echo unitTest("dclo@us.ibm.com");
echo unitTest("abc\\@def@example.com");
echo unitTest("abc\\\\@example.com");
echo unitTest("Fred\\ Bloggs@example.com");
echo unitTest("Joe.\\\\Blow@example.com");
echo unitTest("\"Abc@def\"@example.com");
echo unitTest("\"Fred Bloggs\"@example.com");
echo unitTest("customer/department=shipping@example.com");
echo unitTest("\$A12345@example.com");
echo unitTest("!def!xyz%abc@example.com");
echo unitTest("_somename@example.com");
echo unitTest("user+mailbox@example.com");
echo unitTest("peter.piper@example.com");
echo unitTest("Doug\\ \\\"Ace\\\"\\ Lovell@example.com");
echo unitTest("\"Doug \\\"Ace\\\" L.\"@example.com");
echo unitTest("abc@def@example.com", "Doug Lovell says this should fail");
echo unitTest("abc\\\\@def@example.com", "Doug Lovell says this should fail");
echo unitTest("abc\\@example.com", "Doug Lovell says this should fail");
echo unitTest("@example.com", "Doug Lovell says this should fail");
echo unitTest("doug@", "Doug Lovell says this should fail");
echo unitTest("\"qu@example.com", "Doug Lovell says this should fail");
echo unitTest("ote\"@example.com", "Doug Lovell says this should fail");
echo unitTest(".dot@example.com", "Doug Lovell says this should fail");
echo unitTest("dot.@example.com", "Doug Lovell says this should fail");
echo unitTest("two..dot@example.com", "Doug Lovell says this should fail");
echo unitTest("\"Doug \"Ace\" L.\"@example.com", "Doug Lovell says this should fail");
echo unitTest("Doug\\ \\\"Ace\\\"\\ L\\.@example.com", "Doug Lovell says this should fail");
echo unitTest("hello world@example.com", "Doug Lovell says this should fail");
echo unitTest("gatsby@f.sc.ot.t.f.i.tzg.era.l.d.", "Doug Lovell says this should fail");
?>
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