Validate an email address by checking its syntax and if the given domain exists

ValidateEmail.php

<?php

  if (function_exists(real_email)) {
    
    /**
     * Validate an email address by checking its syntax
     * and if the given domain exists
     *
     * @param   string $email  The email address
     * @return  bool
     */
    function real_email(string $email, bool $debug = false): bool
    {
        preg_match("/^(?:.*)@(.*)$/", $email, $matches);§
        $host = $matches[0];
        
        if ($host && ! filter_var($email, FILTER_VALIDATE_EMAIL)) {
            return false;
        }

        if ($debug) {
            return true;
        }
        
        return checkdnsrr(idn_to_ascii($host), 'MX');
    }
    
  }