Script works with PHP 5.4.16, but not PHP 5.3.3... where is the faulty code?

Script works with PHP 5.4.16, but not PHP 5.3.3... where is the faulty code?

I'm a beginner in php, and... I was just trying to create this... dynamic
indexing/document_display script using php... What I was trying to do
isn't really important to the question, however. The thing is... my script
does exactly what I want it to do, when hosted on a WAMP server with php
5.4.16... but when uploaded to a LAMP server with php 5.3.3, I get the
error
Fatal error: Can't use function return value in write context in
/users/clentz/testphpindex.php on line 34
I need it to work on this lamp server.
Can anyone tell me what about the following code is causing errors with
the php 5.3.3 interpreter?
<?php
$courses_directory = "./Courses";
$courses_array = scandir($courses_directory);
if (empty($_SERVER['QUERY_STRING']))
{
include 'Misc/common_components/headers/index_header.html';
echo "\r\n\t<h1>Enrolled Courses</h1>";
for ($uwmi_loop_var = 2; isset($courses_array[$uwmi_loop_var]);
$uwmi_loop_var++)
{
if ($uwmi_loop_var == 2)
{
echo "\r\n\t<ul>";
}
if (isset($courses_array[$uwmi_loop_var]))
{
echo "\r\n\t\t<li>" . '<a href="?' .
$courses_array[$uwmi_loop_var] . '">' .
$courses_array[$uwmi_loop_var] . '</a></li>';
}
if (!isset($courses_array[($uwmi_loop_var + 1)]))
{
echo "\r\n\t</ul>\r\n";
}
}
include 'Misc/common_components/footer.html';
}
else if (!empty($_SERVER['QUERY_STRING']))
{
for ($uwmi_loop_var = 2; isset($courses_array[$uwmi_loop_var]);
$uwmi_loop_var++)
{
if (explode("&",$_SERVER['QUERY_STRING'])[0] ==
rawurlencode($courses_array[$uwmi_loop_var]))
{
include "./Courses/" . $courses_array[$uwmi_loop_var] .
"/index.php";
}
}
}
?>
If it helps, you can see the code in a little more visually appealing
format at: pic of the code in a visually appealing format