PHP Regular Expression Validation example code for an email

The regular expression (regular expression) describes a pattern of string matching that can be used to check whether a string contains a seed string, replace a matched substring, or remove a substring from a string that matches a certain condition. This article mainly introduces the PHP regular verification email method, involving PHP regular expression validation of the relevant skills, the need for friends can refer to the following . Specific as follows:

<?phpfunction Validateemail ($email) {$isValid = true; $atIndex = Strrpos ($email, "@"); if (Is_bool ($atIndex) &&amp  ;! $atIndex) {$isValid = false;} else {$domain = substr ($email, $atIndex + 1);  $local = substr ($email, 0, $atIndex);  $localLen = strlen ($local);  $domainLen = strlen ($domain);  if ($localLen < 1 | | $localLen >) {//Local part length exceeded $isValid = false;  } else if ($domainLen < 1 | | $domainLen > 255) {//Domain part length exceeded $isValid = false;  } else if ($local [0] = = '. ' | | $local [$localLen-1] = = '. ')   {//Local part starts or ends with '. '  $isValid = false;  } else if (Preg_match ('/\\.\\./', $local)) {//Local part has both consecutive dots $isValid = false; } else if (!preg_match ('/^[a-za-z0-9\\-\\.  +$/', $domain)) {//character not valid on domain part $isValid = false;  } else if (Preg_match ('/\\.\\./', $domain)) {//Domain part has both consecutive dots $isValid = false; } else if (!preg_maTCH ('/^ (\\\\.| [a-za-z0-9!#%& ' _=\\/$\ ' *+?^{}|~.-]) +$/', Str_replace ("\\\\", "", $local))) {//character not valid on local part unless//local-is quoted if (!p Reg_match ('/^ ' (\\\\ "|[   ^ "]) +" $/", Str_replace (" \\\\ "," ", $local))) {$isValid = false; }} if ($isValid &&! ( CHECKDNSRR ($domain, "MX") | |  CHECKDNSRR ($domain, "A"))) {//Domain not found in DNS $isValid = false; }} return $isValid;}? >