How umask Function Works in PHP

Umask function subtracts permissions for files and directories on creation.

Permission values:
0 = --- no permission
1 = --x execute
2 = -w- write
3 = -wx write and execute
4 = r-- read
5 = r-x read and execute
6 = rw- read and write
7 = rwx read, write and execute

<?php

// default 0644 = rw-r--r--
// we want 0400 = r--------
// 0777 - 0400 = 0377
umask(0377);

// The file will be created with permissions 0400
fopen('test.txt', 'w');