Code works on appserver and xampp(localhost) but not on my website

I've coded a forum via php on my localhost(appserv and xampp). But when i try to publish my code on my webiste i get HTTP ERROR 500(https://gyazo.com/0ecdb91efa5d2b256416ecc0e7031dc8, Site dosen't work).

This site is made to check when the user click the login button, if the user exists and what role the user has. Then set a session to the value, if the user is logged in or not and what role the user has.

<?php
    if(isset($_POST['submitlogin'])) {

    $link = mysqli_connect('secret', 'secret', 'secret', 'secret');

    if(!$link) {
      echo 'We are having trouble connecting to the database.';
      exit;
    }
    $userLogin = $_POST['usernamelogin'];
    $passLogin = $_POST['passwordlogin'];

    $query = "SELECT * FROM personinfo WHERE Name='$userLogin' and Password='$passLogin'";
    $result = mysqli_query($link, $query);

    $posts = mysqli_fetch_all($result, MYSQLI_ASSOC);

    foreach ($posts as $post)
    {
      if ($userLogin == $post['Name'] && $passLogin == $post['Password']) {
          session_start();
          $_SESSION['login'] = $userLogin;
          $_SESSION['loginpass'] = $passLogin;
          if ($post['Administrator'] == 1) {
            $_SESSION['Admin'] = '1';
          }
          else if ($post['Moderator'] == 1) {
            $_SESSION['Mod'] = '1';
          }
          echo 'Correct information';
        }
      header("refresh:0; url=../");
    }
}