It seems happened since introduction of php 5.3.0. If you see in the changelogs:

http://www.php.net/ChangeLog-5.php

Added support for ACL (is_writable, is_readable, reports now correct results) on Windows. (Pierre, Venkat Raman Don, Kanwaljeet Singla)

This issue is very critical, because it makes php running on windows production server impractical / unusable...

My quad xeon box becomes very slow after some days, the ram usage is mysteriously increased (httpd process usage still remains the same, I thought handle consumes kernel spaces)...

If your webserver servers 1 million request, then there will be about 1 million handle opened... Usual application only consumes 20 to 2000 handles...

Memory leak confirmed for the following configurations:

PHP vc9 5.3.15, thread safe version + Apache Httpd 2.4.2 + Win XP SP3 
PHP vc9 5.4.5,  thread safe version + Apache Httpd 2.4.2 + Win XP SP3 

Running Test script:
--------------------
for($i=0; $i<100;$i++) {
  is_readable("c:\\temp");
}

PHP vc9 5.4.5 tested on WAMP stacks:
------------------------------------

XAMPP USB Lite 1.8.0        (Windows XP SP3)
Uniform Server 8.5.8-Coral  (Windows XP SP3)

For details see:
http://forum.uniformserver.com/index.php?showtopic=2627&hl=

Windows 7 SP1 and Windows Server 2008 R2 (both is 64-bit OS)

I agree with above comment, it makes running PHP on a Windows production server impractical.

Is there any progress? This issue makes PHP really hard to use on Windows.

The problem is in TSRM\tsrm_win32.c in function

TSRM_API int tsrm_win32_access(const char *pathname, int mode TSRMLS_DC)

A local variable 

	HANDLE thread_token;

is being initialized by this call

		if(!OpenThreadToken(GetCurrentThread(), TOKEN_ALL_ACCESS, TRUE, &thread_token)) {

which is likely to succeed, but even if it does not there is another call

				if (!OpenProcessToken(GetCurrentProcess(), TOKEN_ALL_ACCESS, &thread_token)) {

that creates the handle.  

However, no CloseHandle is called, which causes the handle to leak. 

We need to change the code like this

	HANDLE thread_token;
->	
	HANDLE thread_token=NULL;



Finished:
		if(real_path != NULL) {
			free(real_path);
			real_path = NULL;
		}
->
Finished:
		if (thread_token) CloseHandle(thread_token);

		if(real_path != NULL) {
			free(real_path);
			real_path = NULL;
		}

according to the msdn, the fix is okey to me, merged.

" Remarks
Tokens with the anonymous impersonation level cannot be opened.
Close the access token handle returned through the TokenHandle parameter by 
calling CloseHandle. "

http://msdn.microsoft.com/en-us/library/windows/desktop/aa379296(v=vs.85).aspx