How to check if an email address is valid in PHP

To test an email address if valid is not as easy as it seems.

Here is a function that can do this partially : by validating its format and then by checking if the domain it uses has any MX records registered on the DNS.

function checkEmail($email){
	//check email format
	if (filter_var($email, FILTER_VALIDATE_EMAIL) == $email){
		//check if the domain has MX entries
		$aux = explode('@',$email);
		return checkdnsrr($aux[1],'MX');
	}
	return false;
}

What isn't covered in this check :

• There is no check that the actual username really exists.

If you are on Windows hosting you need to add the next 2 functions as well, as the checkdnsrr function isn't native available here :

//THESE FUNCTIONS WERE TAKEN FROM PHP.NET WEBSITE
function win_checkdnsrr($host, $type='MX') {
    $types=array('A', 'MX', 'NS', 'SOA', 'PTR', 'CNAME', 'AAAA', 'A6', 'SRV',
'NAPTR', 'TXT', 'ANY');
    if (!in_array($type,$types)) {
        user_error("checkdnsrr() Type '$type' not supported", E_USER_WARNING);
        return;
    }
    @exec('nslookup -type='.$type.' '.escapeshellcmd($host), $output);
    foreach($output as $line){
        if (preg_match('/^'.$host.'/',$line)) { return true; }
    }
	return false;
}
 
 
function checkdnsrr($host, $type='MX') {
	return win_checkdnsrr($host, $type);
}