When should I use a bitwise operator?

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Bitwise is useful for things in PHP just like anything else.

How about a value that can have multiple states turned on at the same time?

<?php

// since we're setting constant values in base10 we must progressively double
// them since bitwise operations work in base2. you'll see why when we output
// these as binary values below.
const STATE_FOO = 1;
const STATE_BAR = 2;
const STATE_FEZ = 4;
const STATE_BAZ = 8;

// show base2 values of the above constants
echo sprintf("STATE_FOO's base2 value is %08d\n", decbin(STATE_FOO));
echo sprintf("STATE_BAR's base2 value is %08d\n", decbin(STATE_BAR));
echo sprintf("STATE_FEZ's base2 value is %08d\n", decbin(STATE_FEZ));
echo sprintf("STATE_BAZ's base2 value is %08d\n\n", decbin(STATE_BAZ));

// set state to FOO and FEZ
$state = STATE_FOO | STATE_FEZ;

echo sprintf("base10 value of \$state is %s\n", $state);
echo sprintf("base2 value of \$state is %08d\n", decbin($state));
echo sprintf("Does \$state include FOO state? %s\n", (bool)($state & STATE_FOO));
echo sprintf("Does \$state include BAR state? %s\n", (bool)($state & STATE_BAR));
echo sprintf("Does \$state include FEZ state? %s\n", (bool)($state & STATE_FEZ));
echo sprintf("Does \$state include BAZ state? %s\n", (bool)($state & STATE_BAZ));
echo sprintf("Is state equivalent to FOO and FEZ states? %s\n", ($state == (STATE_FOO | STATE_FEZ)));

Output:

STATE_FOO's base2 value is 00000001
STATE_BAR's base2 value is 00000010
STATE_FEZ's base2 value is 00000100
STATE_BAZ's base2 value is 00001000

base10 value of $state is 5
base2 value of $state is 00000101
Does $state include FOO state? 1
Does $state include BAR state?
Does $state include FEZ state? 1
Does $state include BAZ state?
Is state equivalent to FOO and FEZ states? 1

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