为什么id不会通过链接？ [关闭]

Question

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;

Answer 1

<a class='section_header' href="category/index.php?id=<?php echo $catid?>"><b><?php echo $row[0];?></b></a>