php电子邮件验证函数

<?php function validateEmail($email){    $isValid = true;    $atIndex = strrpos($email, "@");    if (is_bool($atIndex) && !$atIndex){       $isValid = false;    }else{       $domain = substr($email, $atIndex+1);       $local = substr($email, 0, $atIndex);       $localLen = strlen($local);       $domainLen = strlen($domain);       if ($localLen < 1 || $localLen > 64)       {          // 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 two consecutive dots          $isValid = false;       }else if (!preg_match('/^[A-Za-z0-9\\-\\.]+$/', $domain)){          // character not valid in domain part          $isValid = false;       }else if (preg_match('/\\.\\./', $domain)){          // domain part has two consecutive dots          $isValid = false;       }else if(!preg_match('/^(\\\\.|[A-Za-z0-9!#%&`_=\\/$\'*+?^{}|~.-])+$/',str_replace("\\\\","",$local))){          // character not valid in local part unless           // local part is quoted          if (!preg_match('/^"(\\\\"|[^"])+"$/',str_replace("\\\\","",$local))){             $isValid = false;          }       }       if ($isValid && !(checkdnsrr($domain,"MX") || checkdnsrr($domain,"A"))){          // domain not found in DNS          $isValid = false;       }    }    return $isValid; } ?>