PHP code to verify the validity and correctness of the email entered by the user

function validate_email($email){
$exp="^[a-z'0-9]+([._-][a-z'0 -9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";
if(eregi($exp,$email)){ / /First use regular expressions to verify the validity of the email format
if(checkdnsrr(array_pop(explode("@",$email)),"MX")){//Then use checkdnsrr to verify the validity of the domain name part of the email
 return true;
}else{
 return false;
}
}else{
 return false;
}
}
//Note: The checkdnsrr function is invalid on the win host! Below It is a solution proposed by a foreign programmer. He wrote a function to replace the checkdnsrr function:
function myCheckDNSRR($hostName, $recType=''){
if(!emptyempty($hostName)){
if( $ recType=='' ) $recType="MX";
 exec("nslookup -type=$recType $hostName", $result);
 foreach($result as $line){
 if(eregi("^$hostName ",$line)){
 return true;
}
}
return false;
}
return false;
}