Writing files on Linux

Does anybody know why the function below does not work on Linux yet works perfectly well on windows. function write_file($file, $contents){ // $contents is like "Test, Test" global $root_path; // $root_path is /var/www/htdocs $file_location = $root_path.$file; // $file is /jim.txt $fp = fopen("$file_location", "w") or die("Could not open file pointer."); $worked = fwrite($fp, $contents) or die("Could not write to file pinter"); // It fails here fclose($fp) or die("Could not close file pointer"); return $worked; } It always fails at fwrite. Thanks, Corin Rathbone