PHP Code: Validate Email Address String

A bit of code that will use reqular expressions to
validate an email address.

URL: http://snippets.dzone.com/posts/show/4022

<?

function validate_email($email){

$exp = "^[a-z\'0-9]+([._-][a-z\'0-9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";

if(eregi($exp,$email)){
if(checkdnsrr(array_pop(explode("@",$email)),"MX")){
print("$email is ok.
");
}else{
print("$email is ok. But domain is not.
");
}
}else{
print("$email is not ok.
");
}
}

validate_email("shantanu.ok");
validate_email("shantanu.ok@gmail.com");
validate_email("shantanu.ok@fsjaldkfjlsfjsljflsfjsldk.com");

?>