Passing file download via php very slow

Question

Hello,

I have a window 2003 dedicated server, i have installed xampp on it.

So i tried to pass download using PHP script such as zina from pancake.org, phpIndexer php functions such as fread, fgets, file, file_get_contents;

If i download let say from apache mod_dirlisting, the speed is 1mbps however on same server with using php, the speed dropped to 30kbps.

Any idea what causing it? should i tweak any php.ini to reflect?