Form submission giving me a server error - php

Question

I've tried looking for the problem but I can't seem to figure it out. The form shows with no errors, but on google chrome it just says "Server Error" when I try and submit the form.
<?php
if (empty($_GET["entries"])) //check if the admin entered # of weeks
{
?>
<p>How many weeks do you want to make? </p>
<form action="" method="get">
<input type="text" name="entries" placeholder="Number of weeks" />
<br/>
<input type="submit" name="submit_entries" />
</form>
<?php
}
else
{
//Second form
if (isset($_POST["submit"])) //check if submitted
{
//Process form
$entries=$_GET['entries'];
$newWeeks=$_POST['week'];
$db= mysql_connect("localhost", "root", "root");
if(!$db) die("Error connecting to MySQL database.");
mysql_select_db("onlineform", $db);
$sql = "INSERT INTO onlineformdata (numberOfWeeks, newCampSessions) VALUES (" . PrepSQL($entries) . "," . PrepSQL($newWeeks) . ")";
mysql_query($sql);
if (mysql_query($sql) === FALSE) {
die(mysql_error());
}
mysql_close();
}
else //if not submitted yet, show the form
{
echo '<form action="" method="post">';
for ($count = 0; $count < $_GET["entries"]; $count++)
{
echo 'Enter a beginning to ending date for the week: <input type="text" name="week"><br/>';
}
echo '<input type="submit" name="submit"></form>';
}
}
?>
Maybe it's because I can't have the first form having an action pointing to itself (Where I'm using a method="get".

Answer 1

You don't appear to have defined the PrepSQL() anywhere. If that's the case you should be getting a fatal error, something like
Fatal error: Call to undefined function PrepSQL ...
Once that's fixed, if you're insert query is failing, it will probably be because of the values lacking enclosing quotes.
For future debugging you can turn errors on:
error_reporting(E_ALL);
ini_set('display_errors', '1');
Or you can just observe your server's error log. How that is done depends on the server setup so I suggest asking your host for directions.
Side note:
The mysql_* library is deprecated, consider upgrading to PDO or MySQLi
The use of a Prepared Statement is preferred to concatenating variables into your SQL.