php code only work if files has been changed - php

Question

The variable in the session only changes if i update the file meaning:
<?php
if(isset($_GET['row']) && isset($_GET['quantity'])) {
if($_GET['quantity'] != 0) {
$_SESSION['basket'][$_GET['row']]['barcode']['quantity'] = $_GET['quantity'];
} else {
unset($_SESSION['basket'][$_GET['row']]);
}
}
?>
Changes the quantity first time and then in other tries doesn't.
If I change it to something like:
<?php
if(isset($_GET['row']) && isset($_GET['quantity'])) {
if($_GET['quantity'] != 0) {
$num = $_GET['quantity'];
$_SESSION['basket'][$_GET['row']]['barcode']['quantity'] = $num;
} else {
unset($_SESSION['basket'][$_GET['row']]);
}
}
?>
I save the file in works once and then it stops changing the quantity.
When echoing the variable in the code in shows that it's changed but in the rest of the site it doesn't. the part where it shows doesn't manipulate the variables only prints them.
It seems as if the code works only if the file's been saved and only for the first time.
Thanks in advance.