How to validate an email address in PHP

Question

I have this function to validate an email addresses:

function validateEMAIL($EMAIL) {
    $v = "/[a-zA-Z0-9_-.+]+@[a-zA-Z0-9-]+.[a-zA-Z]+/";

    return (bool)preg_match($v, $EMAIL);
}

Is this okay for checking if the email address is valid or not?

Answer 1

If you want to check if provided domain from email address is valid, use something like:

/*
* Check for valid MX record for given email domain
*/
if(!function_exists('check_email_domain')){
    function check_email_domain($email) {
        //Get host name from email and check if it is valid
        $email_host = explode("@", $email);     
        //Add a dot to the end of the host name to make a fully qualified domain name and get last array element because an escaped @ is allowed in the local part (RFC 5322)
        $host = end($email_host) . "."; 
        //Convert to ascii (http://us.php.net/manual/en/function.idn-to-ascii.php)
        return checkdnsrr(idn_to_ascii($host), "MX"); //(bool)       
    }
}

This is handy way to filter a lot of invalid email addresses, along with standart email validation, because valid email format does not mean valid email.

Note that idn_to_ascii() (or his sister function idn_to_utf8()) function may not be available in your PHP installation, it requires extensions PECL intl >= 1.0.2 and PECL idn >= 0.1.

Also keep in mind that IPv4 or IPv6 as domain part in email (for example user@[IPv6:2001:db8::1]) cannot be validated, only named hosts can.

See more here.

Answer 2

/(?![[:alnum:]]|@|-|_|\.)./

Nowadays, if you use a HTML5 form with type=email then you're already by 80% safe since browser engines have their own validator. To complement it, add this regex to your preg_match_all() and negate it:

if (!preg_match_all("/(?![[:alnum:]]|@|-|_|\.)./",$email)) { .. }

Find the regex used by HTML5 forms for validation
https://regex101.com/r/mPEKmy/1

Answer 3

You can use filter_var for this.

<?php
   function validateEmail($email) {
      return filter_var($email, FILTER_VALIDATE_EMAIL);
   }
?>