Simply umask means the default permissions for new files/directories:
<?php
umask(022);
?>
This sets the default permissions for user, groups, and others respectively:
• 0 - read, write and execute
• 1 - read and write
• 2 - read and execute
• 3 - read only
• 4 - write and execute
• 5 - write only
• 6 - execute only
• 7 - no permissions