PHP My SQL Database table not visible - php

Question

I am beginner to PHP and mySQL. I am creating a navigation trough my database. I have two tables set up one is the main nav items and one is the sub nav items. They are connected by the subject_id. I am using a loop to display them. The first table displays and the second table leaves space for where the information should be but it does not show up. I think it must be something in the SQL settings but I have no idea. Here is my code(i know the database is connected):
<?php require_once("includes/connection.php") ?>
<?php require_once("includes/functions.php") ?>
<?php include("includes/headder.php") ?>
<table id="structure">
<tr>
<td id="navigation">
<ul class="subjects">
<?php
$subject_set = mysql_query("SELECT * FROM subjects", $connection);
if(!$subject_set){
die("database query failed: " . mysql_error());
}
while ($subject = mysql_fetch_array($subject_set)) {
echo "<li>" . $subject["menu_name"] . "</li>";
$page_set = mysql_query("SELECT * FROM pages WHERE subject_id = {$subject["id"]}", $connection);
if(!$page_set){
die("database query failed: " . mysql_error());
}
echo "<ul class=\"pages\">";
while ($page = mysql_fetch_array($page_set)) {
echo "<li>" . $page["menu_name"] . "</li>";
}
echo "</ul>";
}
?>
</ul>
</td>
<td id="page">
<h2>Content Area</h2>
</td>
</tr>
</table>
<?php include("includes/footer.php") ?>

Answer 1

Since you mentioned that white space is showing where the data should be, it appears that rows are indeed found. Consequently, your select statement should be ok. This most likely means that the index "menu_name" can't be found on the $page record.
Check to make sure that "menu_name" is indeed a column of the pages table.
To test what valid columns the $page record has you can use the following inside the while $page loop:
var_dump($page);
If the subject id is an integer you do not need single quotes in the where clause. However, if the subject_id contains any non-integer characters, your select statement would need to be:
$page_set = mysql_query("SELECT * FROM pages WHERE subject_id = '{$subject["id"]}'", $connection);