A response to the note below:Your function is also useless, as the WinNT 32 kernel only functions at a minimum of about 10+ ms (1,000 us), rendering usleep() useless, because usleep uses the C function which is provided by the system (in this case, kernel32.dll).You'll want to use a function that does not rely on the kernel, but rather something made for precise measurement:<?phpfunction usleep_win( $micro_seconds ){ if ( @function_exists( "socket_create" ) && @function_exists( "socket_select" ) ) { $false = NULL; $socket = array( socket_create( AF_INET, SOCK_RAW, $false ) ); socket_select( $false, $false, $socket, 0, $micro_seconds ); return true; } else { return false; }}?>This function will allow to you sleep for a specified microsecond, although I have measured it to be off by ~5 us.Again, most of this depends on the hardware in your system. If you _REALLY_ need to be precise to < 10 us, you shouldn't be using WinNT anyways!