用PHP验证邮箱有效性

<?php

function validate_email($email){
$exp = "^[a-z'0-9]+([._-][a-z'0-9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";
if(eregi($exp,$email)){ //先用正则表达式验证email格式的有效性
if(checkdnsrr(array_pop(explode("@",$email)),"MX")){//再用checkdnsrr验证email的域名部分的有效性
return true;
}else{
return false;
}
}else{
return false;
}
}

?>

function myCheckDNSRR($hostName, $recType = '') {
if(!empty($hostName)) {
if( $recType == '' ) $recType = "MX";
exec("nslookup -type=$recType $hostName", $result);
// check each line to find the one that starts with the host
// name. If it exists then the function succeeded.
foreach ($result as $line) {
if(eregi("^$hostName",$line)) {
return true;
}
}
// otherwise there was no mail handler for the domain
return false;
}
return false;
}