Алексей

$str = '11223344556677';
echo preg_replace('/(\d{2})(\d{4})(\d{4})(\d{4})/', '$1 $2 $3 $4', $str);

var xhr = new XMLHttpRequest();
xhr.open("get", "https://site2.example.com/?g=x", true);
xhr.send();

SELECT *
FROM `table` 
WHERE (
    `size` LIKE '36|%' OR
    `size` LIKE '%|36|%' OR
    `size` LIKE '%|36'
)

select LPAD(id,6,'0') from table order by id desc limit 1;

function user_is_authorized($user) {
  $is_authorized = false;

  if (isset($user)) {
    $is_authorized = true; // удостоверьтесь, что пользователь авторизован
  }

  return $is_authorized;
}

if (user_is_authorized($user) && isset($file['down_rating']) && isset($user['rating']) && $file['down_rating'] <= $user['rating'] && ((isset($user['fraudster']) && $user['fraudster'] == 0) || (!isset($file['id_category']) || $file['id_category'] != 3)))
{
//download
}