This Code helps you: Php validation for a inputed email 

function is_valid_email($email) {
$result = TRUE;
if(!eregi(“^[_a-z0-9-]+(.[_a-z0-9-]+)*@[a-z0-9-]+(.[a-z0-9-]+)*(.[a-z]{2,4})$”, $email)) {
$result = FALSE;
}
return $result;
}