I have a simple link that needs to pass a variable through $_GET and set it to a variable in the page that is being opened. It is failing every time however and I am not sure why.
<a class='section_header' href='category/index.php?`id='" . $catid . "'><b>" . $row[0] ."</b></a>
Code in category/index.php
$id = $_GET['id'];
echo $id;
<a class='section_header' href="category/index.php?id=<?php echo $catid?>"><b><?php echo $row[0];?></b></a>
Try
<a class='section_header' href='category/index.php?id='" . $catid . "'><b>" . $row[0] ."</b></a>
You had a random ` in there. Once it prints out you can use inspect element to make sure the url looks correct and id is populated.