filemtime -help

i have a problem with filemtime function, i want script print out the date of file last modified. here is code, $fp=fopen("ex.txt","r"); echo date("j F Y H:i", filemtime($fp)); fclose($fp); it turns out; 1 January 1970 02:00 everytime , i modified file, but this doesnt change, lastly i deleted and uploaded file again, it turns out again 1 January 1970 02:00 . my server date is correct, output for date("j F Y H:i") is 12 December 2002 15:40 operating system is linux, and running apache server. do i need to use clearstatcache ? if so, how? thanks for any assistance