PHP wont write to a file residing on the same location

First, the code:

<?php
$filename = 'survey.txt';
$fp = fopen($filename, "a");
$date = date("l F dS Y h:i:s A");
$domain = GetHostByName($REMOTE_ADDR);
$string = "$date ($domain)\r\nName : $name\r\nSex : $sex\r\nWhich shopping method : $q1\r\nWhy : $q2\r\nRate : $q3\r\nWords : $q4\r\nHow to improve : $q5"."\r\n\r\n";
$write = fputs($fp, $string);
fclose($fp);
?>

When I test this on my local machine, it writes fine. But once I upload it to the server, it wont write at all. The weird thing is that I have a counter script that writes in almost the exact same way, yet it works.

Any Ideas?