This is only the case when stat() fails.

If you change stat('.'); to stat('<some file>'); you will se that PHP5 is faster than php4. Almost 2x.

I have modified the code to use, $blah = stat('.htaccess');
This file does exist, it is 161 bytes on NTFS.

PHP 4.4.6: 1.641ms
PHP 5.1.2: 108.29ms

Normally, I would be using the commands on many small files (400ish) in the current folder to determine if any of them had changed. This was fast enough on PHP4, but on PHP5, the same code takes much longer.

Might be related to stat cache usage... Try to see if you see the difference stat'ing a set of files in random order, not the same file repeatedly.

Here's the new code:

<?
header('Content-type: text/plain');
function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();
$c = 0;
foreach (glob("*.torrent") as $filename) {
    $blah = stat($filename);
    $c++;
}
$time_end = microtime_float();
$time = $time_end - $time_start;
echo 'Took '.round(($time*100),3).'ms for '.$c.' files';
?>
and the results:
PHP 4.4.6
Took 5.232ms for 481 files
PHP 5.2.1
Took 107.762ms for 481 files

One thing I have noticed is that when the PHP5 version runs, Apache2's kernel CPU time shoots up (measured in (Process Explorer) while processing the request where as in PHP4, CPU use remains low.

I have new information, the slowness is present only when safe mode is on.
(for 1000 iterations)
For PHP 4.4.6
-----
G:\>C:\php4\php.exe -n -d safe_mode=On filemtime.php
X-Powered-By: PHP/4.4.6
Content-type: text/plain

Took 7.451ms
G:\>C:\php4\php.exe -n -d safe_mode=Off filemtime.php
X-Powered-By: PHP/4.4.6
Content-type: text/plain

Took 0.152ms
G:\>



For PHP 5.2.1
-----
G:\>C:\php5\php-cgi.exe -n -d safe_mode=On filemtime.php
X-Powered-By: PHP/5.2.1
Content-type: text/plain

Took 12.172ms
G:\>C:\php5\php-cgi.exe -n -d safe_mode=Off filemtime.php
X-Powered-By: PHP/5.2.1
Content-type: text/plain

Took 0.108ms
G:\>


Additionally, I checked with FileMon, and the requests made are different for each version (Safe mode On).

PHP 4.4.6
6:03:02.751 AM	php.exe:2344	OPEN	G:\	SUCCESS	Options: Open Directory  Access: 00100001	
6:03:02.751 AM	php.exe:2344	DIRECTORY	G:\	SUCCESS	FileBothDirectoryInformation: filemtime.php	
6:03:02.751 AM	php.exe:2344	CLOSE	G:\	SUCCESS		

PHP 5.2.1
6:03:04.158 AM	php-cgi.exe:2216	QUERY INFORMATION	G:\filemtime.php	SUCCESS	Attributes: A	
6:03:04.158 AM	php-cgi.exe:2216	OPEN	G:\	SUCCESS	Options: Open Directory  Access: 00100001	
6:03:04.158 AM	php-cgi.exe:2216	DIRECTORY	G:\	SUCCESS	FileBothDirectoryInformation: filemtime.php	
6:03:04.158 AM	php-cgi.exe:2216	CLOSE	G:\	SUCCESS		



note the additional "QUERY INFORMATION" access.


I've tried disabling safe mode and though performance has improved, it is still slower than the PHP4 version on my script when run under an apache module. The stats are now:

~40ms safe mode on (PHP5)
~15ms safe mode off (PHP5)

~5.5ms safe mode on (PHP4)
~0.7ms safe mode off (PHP4)

I tried to run php 4.4.6 vs. php 5.2.1 and on both examples I had PHP 5 faster than PHP 4. Maybe you have some other setting interfering? Try testing with empty php.ini - it would use defaults for both.