stat functions do each path component?

In comparing the performance of PHP 5.2.5 file_exists calls versus C stat calls, I discovered via Windows sysinternals ProcessMonitor that PHP seems to do a stat on each component of a file path. For example, file_exists("e:\\wamp\\www\\ra-v2\\system\\application\\libraries\\MY_Controller.php") appears to stat "E:\wamp", "E:\wamp\www", etc., finally getting to the file. That compares to doing _stat64 of "e:\\wamp\\www\\ra-v2\\system\\application\\libraries\\MY_Controller.php" in C, which just does the stat on the file. The timings from my tests show the C app finishing in about one-seventh the time, which is what I would expect from the PHP code doing seven times as many stat calls. Assuming my inference about all the stat calls is correct, is there a rationale for this? If the PHP app I am working on made just a couple of file_exists calls, I would not bother to ask, but it uses the CodeIgniter framework which is doing >100 file_exists calls for each page being accessed, so the affect is very noticeable. FYI, I poked around the PHP SVN web interface for a while and found php_check_open_basedir_ex called in plain_wrapper.c, which I suspect causes the calls, but ran out of steam before confirming the cause of the behavior. TIA -- Scott Nichol