Why should I use bitwise/bitmask in PHP?

Question

I am working on a user-role / permission system in PHP for a script.

Below is a code using a bitmask method for permissions that I found on phpbuilder.com.

B

Answer 1

problem of this is if PERMISSION_READ is a mask itself

if($ARR_permission & PERMISSION_READ) {
    echo 'Access granted.';
}else {
    echo 'Access denied.';

then for 0101 - $rightWeHave 0011 - $rightWeRequire

it is access granted, which we probably do not want so it should be

if (($rightWeHave & $rightWeRequire) == $rightWeRequire) {
echo 'access granted';
}

so now for

0101 0011

result is

0001 so access is not granted because it is not equal to 0011

but for

1101 0101

it is ok as the result is 0101