Email Validation Using PHP

<?php
function isValidEmail($email){
$pattern = "^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$";
if (eregi($pattern, $email)) {
return 'true';
}
else {
return 'false';
}
}
?>