<?php
session_start();
$id = 'dd';
print_r($_SESSION);
?>
When I go to this page the variable $_SESSION['id'] is defined as a number. But on this page I define the variable $id and then when I print the $_SESSION it has changed the variable $_SESSION['id'] to 'dd'. How is this possible?
There's only two ways for your code to work as stated:
1) You've got register_globals on, and your session already had a id parameter set
That means you're on an OLD php install, and/or a horribly badly configured one. Register_globals is pretty much the single greatest STUPIDITY in the history of PHP, and it has thankfully been eliminated from "modern" versions of PHP.
2) You created a reference beforehand, e.g.
$_SESSION['id'] = 'foo';
$id =& $_SESSION['id']; // $id now points at the session variable
echo $id; // prints foo
$id = 'bar'; // also changes the session value, because of the referencing.
echo $_SESSION['id']; // prints 'bar', because of the referencing.
You have register globals turned on. This causes the declaration of $id to overwrite the $_SESSION['id'] since they point to the same place.
You should turn this off as it is deprecated and can cause issues like you are experiencing.
