PHP $_SESSION nested array is lost when a foreach() dummy name matches array name

Can someone please confirm that the following开发者_开发知识库 is a bug with PHP 5.2.13: (thank you)

<?php
    session_start();
    if (!is_array($_SESSION["breadcrumb"]["trail"]))
    {
        $_SESSION["breadcrumb"]["trail"][] = "trail";
    } 
    foreach ($_SESSION["breadcrumb"]["trail"] as $breadcrumb)
    {
        echo $breadcrumb;
    }
?>

The above PHP script crashes the 3rd time it is run. The foreach() loop seems to have an (improper) side effect which wipes out the nested $_SESSION array because the internal variable used in the loop matches the name of the nested $_SESSION array. Simply changing the name of the internal foreach() variable to something different fixes the problem.

Note: clear session variables before running script 3 times.

Again, changing "$breadcrumb" to "$the_breadcrumb" fixes the problem. But the foreach() loop should have no side effects. Note: since the scope of $breadcrumb is not the same as the scope of $_SESSION["breadcrumb"], there should be no collision.

Note that doing a print_r() on the array shows the array as (correctly) empty the first time, (correctly) populated the second time, and erroneously set as "Array ( [breadcrumb] => trail )" the third time (the nested array has been wiped out).

The error in the PHP error log from the 3rd run: PHP Fatal error: Cannot use string offset as an array on line 5

The issue is not a problem on PHP 5.3 - only PHP 5.2.13. I could not find any note regarding this issue in the PHP changelog on the PHP site (php.net), and I must use 5.2.13 on my live site, so I'm posting here hoping that someone can confirm. I've also posted a bug report on php.net.

Thanks, Dan Nissenbaum

Expected result:

No PHP 5.2.13 crash on line 5.

Actual result:

PHP 5.2.13 crashes on line 5.

Solved. notJim points out the register_globals php.ini setting. It was set to On. Turn to Off to separate the scope, as expected. Note: register_globals is deprecated as of (at least as far back as) PHP 5.3 - probably further back.

Yes this is a definitely a bug. I changed the variable names in my foreach statements to something different than my session variables in order to get both to work properly. This problem does not occur in php version 5.3.0.

I use 5.2.6 and works greet, no error.