Strange File write Problem

The code below works on every server that I have tried it on, till now. On this server it will create the file name but will not write to it. If you create a file and upload it, it will erase everything but not write. Any Ideas why? <?php

                  $filename = "/path/to/file/free.txt";

                 $handle= fopen($filename,'w+');

                fputs($handle, $free);

                fclose($handle);
               ?>

TIA Gary