php exec problem with unzip

I want to upload a zip file and then extract/unzip it. I am accomplishing this with php exec command. I am calling unzip from php exec command within a php script and it is not extracting files. why?
[PHP]<?php
echo exec('unzip file.zip');
?>[/PHP]

i checked apache logs and it says

It works perfectly fine when i unzip using SSH command line..
how to fix this problem.

re: php exec problem with unzip

Make sure you set the file permissions of that folder to 777 or the lowest allowable for the script to work.