I upgraded my installation to Apache 2.0.43 (old was 2.0.36) and PHP 2.4.3 (old was 2.4.1), and noticed that my application doesn't work anymore. PHP is compiled as module.

Finally, I found that file_exists() function doesn't work properly. My test script:

<?php
        $e1 = file_exists("index.php");
        $e2 = is_file("index.php"); 
        echo "e1 = $e1; e2 = $e2";
?>

It's output:

e1 = ; e2 = 1

file_exists(".") always returns 1.

Nothing was changed in configuration after upgrade. I looked into source, and found that code responsible for this functionality was significantly changed, so... Perhaps this is a bug. Serious one.