Why doesn't this PHP code work?
<pre><code>&lt;?php
require_once($_SERVER['DOCUMENT_ROOT'].'/api_config.php');

error_reporting(E_ALL);
ini_set("display_errors", 1);
$loc = $_POST['u'];

//initialize the connection to the database
$config = $config['production'];
$con = mysql_connect($config['db']['host'], $config['db']['username'], $config['db']['password']) or die ("Unable to connect");
mysql_select_db ($config['db']['dbname'], $con) or die ("Unable to select database");
$query = "SELECT `location` FROM `active_users` WHERE name = '$loc'";
$result = mysql_query($query, $con) or die ("Unable to run query");

if (mysql_num_rows($result) &gt; 0) { 
// yes, the user esists
    header("HTTP/1.0 200 Success"); 
    header('Content-Type: text/plain');
} else 
// no, user doesn't exist 
    header("HTTP/1.0 404 Not Found");
    header('Content-Type: text/plain');
} 
mysql_close($con);

?&gt;
</code></pre>

<p>I get a <code>HTTP Error 500 (Internal Server Error):</code> error in my browser.  Why? </p>
