我使用的是 PHP 5.3.10 版本。以下是代码：
<?php
$email = "test@example.c";
if (filter_var($email, FILTER_VALIDATE_EMAIL))
echo "Email: ".$email." correct";
else
echo "email not correct";
?>
它的返回值为："邮件地址：test@example.c" 正确。
我认为只有一个字符的顶级域名是不正确的（根据此列表，我不知道有一个字符长度的TLD：http://data.iana.org/TLD/tlds-alpha-by-domain.txt）。
那么，FILTER_VALIDATE_EMAIL 过滤器是否工作正常？
无效的电子邮件地址
来源 http://en.wikipedia.org/wiki/Email_address
几乎所有的电子邮件验证实现都存在“漏洞”，但 PHP 实现可以正常工作，因为它接受所有常见的电子邮件地址。
更新：
发现于http://www.php.net/manual/en/filter.filters.validate.php
关于没有在域名部分中包含.的“部分”地址，源代码（在ext/filter/logical_filters.c中）中的一条评论这样解释了此拒绝：
* The regex below is based on a regex by Michael Rushton.
* However, it is not identical. I changed it to only consider routeable
* addresses as valid. Michael's regex considers a@b a valid address
* which conflicts with section 2.3.5 of RFC 5321 which states that:
*
* Only resolvable, fully-qualified domain names (FQDNs) are permitted
* when domain names are used in SMTP. In other words, 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. Local nicknames or
* unqualified names MUST NOT be used.
这里有一个指向Michael Rushton的课程链接（链接已损坏，请参见下面的源代码），该课程支持RFC 5321/5322。
<?php
/**
* Squiloople Framework
*
* LICENSE: Feel free to use and redistribute this code.
*
* @author Michael Rushton <michael@squiloople.com>
* @link http://squiloople.com/
* @package Squiloople
* @version 1.0
* @copyright © 2012 Michael Rushton
*/
/**
* Email Address Validator
*
* Validate email addresses according to the relevant standards
*/
final class EmailAddressValidator
{
// The RFC 5321 constant
const RFC_5321 = 5321;
// The RFC 5322 constant
const RFC_5322 = 5322;
/**
* The email address
*
* @access private
* @var string $_email_address
*/
private $_email_address;
/**
* A quoted string local part is either allowed (true) or not (false)
*
* @access private
* @var boolean $_quoted_string
*/
private $_quoted_string = FALSE;
/**
* An obsolete local part is either allowed (true) or not (false)
*
* @access private
* @var boolean $_obsolete
*/
private $_obsolete = FALSE;
/**
* A basic domain name is either required (true) or not (false)
*
* @access private
* @var boolean $_basic_domain_name
*/
private $_basic_domain_name = TRUE;
/**
* A domain literal domain is either allowed (true) or not (false)
*
* @access private
* @var boolean $_domain_literal
*/
private $_domain_literal = FALSE;
/**
* Comments and folding white spaces are either allowed (true) or not (false)
*
* @access private
* @var boolean $_cfws
*/
private $_cfws = FALSE;
/**
* Set the email address and turn on the relevant standard if required
*
* @access public
* @param string $email_address
* @param null|integer $standard
*/
public function __construct($email_address, $standard = NULL)
{
// Set the email address
$this->_email_address = $email_address;
// Set the relevant standard or throw an exception if an unknown is requested
switch ($standard)
{
// Do nothing if no standard requested
case NULL:
break;
// Otherwise if RFC 5321 requested
case self::RFC_5321:
$this->setStandard5321();
break;
// Otherwise if RFC 5322 requested
case self::RFC_5322:
$this->setStandard5322();
break;
// Otherwise throw an exception
default:
throw new Exception('Unknown RFC standard for email address validation.');
}
}
/**
* Call the constructor fluently
*
* @access public
* @static
* @param string $email_address
* @param null|integer $standard
* @return EmailAddressValidator
*/
public static function setEmailAddress($email_address, $standard = NULL)
{
return new self($email_address, $standard);
}
/**
* Validate the email address using a basic standard
*
* @access public
* @return EmailAddressValidator
*/
public function setStandardBasic()
{
// A quoted string local part is not allowed
$this->_quoted_string = FALSE;
// An obsolete local part is not allowed
$this->_obsolete = FALSE;
// A basic domain name is required
$this->_basic_domain_name = TRUE;
// A domain literal domain is not allowed
$this->_domain_literal = FALSE;
// Comments and folding white spaces are not allowed
$this->_cfws = FALSE;
// Return the EmailAddressValidator object
return $this;
}
/**
* Validate the email address using RFC 5321
*
* @access public
* @return EmailAddressValidator
*/
public function setStandard5321()
{
// A quoted string local part is allowed
$this->_quoted_string = TRUE;
// An obsolete local part is not allowed
$this->_obsolete = FALSE;
// Only a basic domain name is not required
$this->_basic_domain_name = FALSE;
// A domain literal domain is allowed
$this->_domain_literal = TRUE;
// Comments and folding white spaces are not allowed
$this->_cfws = FALSE;
// Return the EmailAddressValidator object
return $this;
}
/**
* Validate the email address using RFC 5322
*
* @access public
* @return EmailAddressValidator
*/
public function setStandard5322()
{
// A quoted string local part is disallowed
$this->_quoted_string = FALSE;
// An obsolete local part is allowed
$this->_obsolete = TRUE;
// Only a basic domain name is not required
$this->_basic_domain_name = FALSE;
// A domain literal domain is allowed
$this->_domain_literal = TRUE;
// Comments and folding white spaces are allowed
$this->_cfws = TRUE;
// Return the EmailAddressValidator object
return $this;
}
/**
* Either allow (true) or do not allow (false) a quoted string local part
*
* @access public
* @param boolean $allow
* @return EmailAddressValidator
*/
public function setQuotedString($allow = TRUE)
{
// Either allow (true) or do not allow (false) a quoted string local part
$this->_quoted_string = $allow;
// Return the EmailAddressValidator object
return $this;
}
/**
* Either allow (true) or do not allow (false) an obsolete local part
*
* @access public
* @param boolean $allow
* @return EmailAddressValidator
*/
public function setObsolete($allow = TRUE)
{
// Either allow (true) or do not allow (false) an obsolete local part
$this->_obsolete = $allow;
// Return the EmailAddressValidator object
return $this;
}
/**
* Either require (true) or do not require (false) a basic domain name
*
* @access public
* @param boolean $allow
* @return EmailAddressValidator
*/
public function setBasicDomainName($allow = TRUE)
{
// Either require (true) or do not require (false) a basic domain name
$this->_basic_domain_name = $allow;
// Return the EmailAddressValidator object
return $this;
}
/**
* Either allow (true) or do not allow (false) a domain literal domain
*
* @access public
* @param boolean $allow
* @return EmailAddressValidator
*/
public function setDomainLiteral($allow = TRUE)
{
// Either allow (true) or do not allow (false) a domain literal domain
$this->_domain_literal = $allow;
// Return the EmailAddressValidator object
return $this;
}
/**
* Either allow (true) or do not allow (false) comments and folding white spaces
*
* @access public
* @param boolean $allow
* @return EmailAddressValidator
*/
public function setCFWS($allow = TRUE)
{
// Either allow (true) or do not allow (false) comments and folding white spaces
$this->_cfws = $allow;
// Return the EmailAddressValidator object
return $this;
}
/**
* Return the regular expression for a dot atom local part
*
* @access private
* @return string
*/
private function _getDotAtom()
{
return "([!#-'*+\/-9=?^-~-]+)(?>\.(?1))*";
}
/**
* Return the regular expression for a quoted string local part
*
* @access private
* @return string
*/
private function _getQuotedString()
{
return '"(?>[ !#-\[\]-~]|\\\[ -~])*"';
}
/**
* Return the regular expression for an obsolete local part
*
* @access private
* @return string
*/
private function _getObsolete()
{
return '([!#-\'*+\/-9=?^-~-]+|"(?>'
. $this->_getFWS()
. '(?>[\x01-\x08\x0B\x0C\x0E-!#-\[\]-\x7F]|\\\[\x00-\xFF]))*'
. $this->_getFWS()
. '")(?>'
. $this->_getCFWS()
. '\.'
. $this->_getCFWS()
. '(?1))*';
}
/**
* Return the regular expression for a domain name domain
*
* @access private
* @return string
*/
private function _getDomainName()
{
// Return the basic domain name format if required
if ($this->_basic_domain_name)
{
return '(?>' . $this->_getDomainNameLengthLimit()
. '[a-z\d](?>[a-z\d-]*[a-z\d])?'
. $this->_getCFWS()
. '\.'
. $this->_getCFWS()
. '){1,126}[a-z]{2,6}';
}
// Otherwise return the full domain name format
return $this->_getDomainNameLengthLimit()
. '([a-z\d](?>[a-z\d-]*[a-z\d])?)(?>'
. $this->_getCFWS()
. '\.'
. $this->_getDomainNameLengthLimit()
. $this->_getCFWS()
. '(?2)){0,126}';
}
/**
* Return the regular expression for an IPv6 address
*
* @access private
* @return string
*/
private function _getIPv6()
{
return '([a-f\d]{1,4})(?>:(?3)){7}|(?!(?:.*[a-f\d][:\]]){8,})((?3)(?>:(?3)){0,6})?::(?4)?';
}
/**
* Return the regular expression for an IPv4-mapped IPv6 address
*
* @access private
* @return string
*/
private function _getIPv4MappedIPv6()
{
return '(?3)(?>:(?3)){5}:|(?!(?:.*[a-f\d]:){6,})(?5)?::(?>((?3)(?>:(?3)){0,4}):)?';
}
/**
* Return the regular expression for an IPv4 address
*
* @access private
* @return string
*/
private function _getIPv4()
{
return '(25[0-5]|2[0-4]\d|1\d{2}|[1-9]?\d)(?>\.(?6)){3}';
}
/**
* Return the regular expression for a domain literal domain
*
* @access private
* @return string
*/
private function _getDomainLiteral()
{
return '\[(?:(?>IPv6:(?>'
. $this->_getIPv6()
. '))|(?>(?>IPv6:(?>'
. $this->_getIPv4MappedIPv6()
. '))?'
. $this->_getIPv4()
. '))\]';
}
/**
* Return either the regular expression for folding white spaces or its backreference
*
* @access private
* @param boolean $define
* @return string
*/
private function _getFWS($define = FALSE)
{
// Return the backreference if $define is set to FALSE otherwise return the regular expression
if ($this->_cfws)
{
return !$define ? '(?P>fws)' : '(?<fws>(?>(?>(?>\x0D\x0A)?[\t ])+|(?>[\t ]*\x0D\x0A)?[\t ]+)?)';
}
}
/**
* Return the regular expression for comments
*
* @access private
* @return string
*/
private function _getComments()
{
return '(?<comment>\((?>'
. $this->_getFWS()
. '(?>[\x01-\x08\x0B\x0C\x0E-\'*-\[\]-\x7F]|\\\[\x00-\x7F]|(?P>comment)))*'
. $this->_getFWS()
. '\))';
}
/**
* Return either the regular expression for comments and folding white spaces or its backreference
*
* @access private
* @param boolean $define
* @return string
*/
private function _getCFWS($define = FALSE)
{
// Return the backreference if $define is set to FALSE
if ($this->_cfws && !$define)
{
return '(?P>cfws)';
}
// Otherwise return the regular expression
if ($this->_cfws)
{
return '(?<cfws>(?>(?>(?>'
. $this->_getFWS(TRUE)
. $this->_getComments()
. ')+'
. $this->_getFWS()
. ')|'
. $this->_getFWS()
. ')?)';
}
}
/**
* Establish and return the valid format for the local part
*
* @access private
* @return string
*/
private function _getLocalPart()
{
// The local part may be obsolete if allowed
if ($this->_obsolete)
{
return $this->_getObsolete();
}
// Otherwise the local part must be either a dot atom or a quoted string if the latter is allowed
if ($this->_quoted_string)
{
return '(?>' . $this->_getDotAtom() . '|' . $this->_getQuotedString() . ')';
}
// Otherwise the local part must be a dot atom
return $this->_getDotAtom();
}
/**
* Establish and return the valid format for the domain
*
* @access private
* @return string
*/
private function _getDomain()
{
// The domain must be either a domain name or a domain literal if the latter is allowed
if ($this->_domain_literal)
{
return '(?>' . $this->_getDomainName() . '|' . $this->_getDomainLiteral() . ')';
}
// Otherwise the domain must be a domain name
return $this->_getDomainName();
}
/**
* Return the email address length limit
*
* @access private
* @return string
*/
private function _getEmailAddressLengthLimit()
{
return '(?!(?>' . $this->_getCFWS() . '"?(?>\\\[ -~]|[^"])"?' . $this->_getCFWS() . '){255,})';
}
/**
* Return the local part length limit
*
* @access private
* @return string
*/
private function _getLocalPartLengthLimit()
{
return '(?!(?>' . $this->_getCFWS() . '"?(?>\\\[ -~]|[^"])"?' . $this->_getCFWS() . '){65,}@)';
}
/**
* Establish and return the domain name length limit
*
* @access private
* @return string
*/
private function _getDomainNameLengthLimit()
{
return '(?!' . $this->_getCFWS() . '[a-z\d-]{64,})';
}
/**
* Check to see if the domain can be resolved to MX RRs
*
* @access private
* @param array $domain
* @return integer|boolean
*/
private function _verifyDomain($domain)
{
// Return 0 if the domain cannot be resolved to MX RRs
if (!checkdnsrr(end($domain), 'MX'))
{
return 0;
}
// Otherwise return true
return TRUE;
}
/**
* Perform the validation check on the email address's syntax and, if required, call _verifyDomain()
*
* @access public
* @param boolean $verify
* @return boolean|integer
*/
public function isValid($verify = FALSE)
{
// Return false if the email address has an incorrect syntax
if (!preg_match(
'/^'
. $this->_getEmailAddressLengthLimit()
. $this->_getLocalPartLengthLimit()
. $this->_getCFWS()
. $this->_getLocalPart()
. $this->_getCFWS()
. '@'
. $this->_getCFWS()
. $this->_getDomain()
. $this->_getCFWS(TRUE)
. '$/isD'
, $this->_email_address
))
{
return FALSE;
}
// Otherwise check to see if the domain can be resolved to MX RRs if required
if ($verify)
{
return $this->_verifyDomain(explode('@', $this->_email_address));
}
// Otherwise return 1
return 1;
}
}
filter_var('"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com',FILTER_VALIDATE_EMAIL) 被接受了，但 postbox@com 没有。我认为这是一个错误。 - Elias Van Ootegema@b 不被视为有效了，尽管我还是认为这个决定在某种程度上也受到了懒惰的驱使...在测试环境中运行 mail('root@localhost'); 并不显得太过分，对吧？ - Elias Van Ootegemfilter_var不将उपयोगकर्ता@उदाहरण.कॉम视为有效的电子邮件地址。 - Sander VisserFILTER_VALIDATE_EMAIL不支持PHP 5.2.14。
有一个用于验证电子邮件地址的PHP类可以在Google Code上找到：
http://code.google.com/p/php-email-address-validation
您可以像这样使用它：
include('EmailAddressValidator.php');
$validator = new EmailAddressValidator;
if ($validator->check_email_address('test@example.org')) {
// Email address is technically valid
} else {
// Email not valid
}
FILTER_VALIDATE_EMAIL 只能告诉您地址格式是否正确。
考虑以下示例：
// "not an email" is invalid so its false.
php > var_export(filter_var("not an email", FILTER_VALIDATE_EMAIL));
false
// "foo@a.com" looks like an email, so it passes even though its not real.
php > var_export(filter_var("foo@a.com", FILTER_VALIDATE_EMAIL));
'foo@a.com'
// "foo@gmail.com" passes, gmail is a valid email server,
// but gmail require more than 3 letters for the address.
var_export(filter_var("foo@gmail.com", FILTER_VALIDATE_EMAIL));
'foo@gmail.com'
FILTER_VALIDATE_EMAIL 只能告诉你什么时候完全错误，而不能告诉你什么时候正确。
你需要使用像 Real Email 这样的服务，它可以进行深入的电子邮件地址验证。
// foo@gmail.com is invalid because gmail require more than 3 letters for the address.
var_export(file_get_contents("https://isitarealemail.com/api/email/validate?email=foo@gmail.com"));
'{"status":"invalid"}'
// foobar@gmail.com is valid
var_export(file_get_contents("https://isitarealemail.com/api/email/validate?email=foobar@gmail.com"));
'{"status":"valid"}'
查看更多，请参见https://docs.isitarealemail.com/how-to-validate-email-addresses-in-php
我选择使用：
<?php
$email =$argv[1];$result= is_valid_email($email); echo $result;
function is_valid_email($email) { return preg_match('/^(([^<>()[\]\\.,;:\s@"\']+(\.[^<>()[\]\\.,;:\s@"\']+)*)|("[^"\']+"))@((\[\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}\])|(([a-zA-Z\d\-]+\.)+[a-zA-Z]{2,}))$/', $email); }
?>
FILTER_VALIDATE_EMAIL是正确的... - Lajos Veres