<?php

$re = "/^[a-z0-9_\\.\\-]+@[a-z0-9_\\.\\-]*[a-z0-9_\\-]+\\.[a-z]{2,4}/"; 
$str = "1231@asdf.com"; 
 
if (!preg_match($re, $str, $matches) ){
	echo 'false';
}
echo 'email ok';