php正则验证邮箱的函数

 function isemail($email) {
  return strlen($email) > 8 && preg_match("/^[-_+.[:alnum:]]+@((([[:alnum:]]|[[:alnum:]][[:alnum:]-]*[[:alnum:]])\.)+([a-z]{2,4})|(([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5])\.){3}([0-9][0-9]?|[0-1][0-9][0-9]|[2][0-4][0-9]|[2][5][0-5]))$/i", $email);
 }
 if(!isemail($_POST['email'])) {
   echo "对不起，验证邮箱地址不正确！";
 exit();
 }
?>