title: php admin session session
body: <p>I'm trying to make an admin account for my website using php. I'm using the following code and I get "500 internal Server Error" I have no idea what i'm doing wrong.
  I have the following php script in my index.php file for admin.</p>
  
  <pre><code>&lt;?php
  session_start();
  if(!isset($_SESSION["manager"])){
      header("Location: admin_login.php");    
      exit(); 
  }
  
  $id = preg_replace('#[^0-9]#i', '',  $_SESSION["id"]);
  $manager = preg_replace('#[^0-9]#i', '', $_SESSION["manager"]);
  $password = preg_replace('#[^A-Za-z0-9]#i', '', $_SESSION["password"]);
  
  include "../scripts/db_connect.php";
  $sql_str = mysql_query("SELECT * FROM admins WHERE userName = '$userName' AND password =       '$password' LIMIT 1");
  $exist_Count = mysql_num_rows('$sql_str');
  
  if($exist_Count == 0){
      header('location: ../index.php');
      exit(); 
  }
  ?&gt;
  </code></pre>
  
  <p>and the following code is for admin_login.php file where I ask the user to sign in
              </p>
  
  <pre><code>&lt;?php
  if(isset($_POST["userName"]) &amp;&amp; isset($_POST["password"])){
      $manager = $_POST["userName"];
      $password = $_POST["password"];
      include "../scripts/db_connect.php";
      $results = mysql_query("SELECT id FROM admins WHERE userName = '$manager' AND password ='$password' LIMIT 1");
  
  $existCount = mysql_num_rows($results);
  if($existCount == 1){
      while($row  = mysql_fetch_array($results)){
          $id = $row["id"];   
      }
      $_SESSION["id"] = $id;
      $_SESSION["manager"] = $manager;
      $_SESSION["password"] = $password;
      header("Location: index.php");
      exit();
  }
  else{
      echo 'Invalid Information';
      exit(); 
      }
  
  }
  ?&gt;
  </code></pre>