bitflags.php

<?php

define('FLAG_0', 1);
define('FLAG_1', 2);
define('FLAG_2', 4);
define('FLAG_3', 8);

/**
 * Will fail when setting multiple flags at once
 */
function setFlag($flag)
{
        global $flags;

        if (($flags & $flag))
        {
                return;
        }

        $flags |= $flag;
}

/**
 * Proper way to do it
 */
function setFlag2($flag)
{
        global $flags;

        if (($flags & $flag) == $flag)
        {
                return;
        }

        $flags |= $flag;
}


function removeFlag($flag)
{
        global $flags;

        $flags ^= $flag;
}

function removeFlag2($flag)
{
        global $flags;

        $flags &= ~$flag;
}

/**
 * This fails on multiple flags
 */
function removeFlag3($flag)
{
        global $flags;

    if (($flags & $flag) == $flag)
    {
                $flags &= ~$flag;
    }
}

/**
 * This works as intended
 */
function removeFlag4($flag)
{
    global $flags;

    if ($flags & $flag)
    {
        $flags &= ~$flag;
    }
}

echo "setting flags \n";

echo "Test 1: setFlag(FLAG_2); start: 0, expecting: 4  \n";
$flags = 0;
setFlag(FLAG_2);
echo "value is $flags \n\n";

echo "Test 2: setFlag(FLAG_1 | FLAG_2); start: 4, expecting: 6 \n";
setFlag(FLAG_1 | FLAG_2);
echo "Value is $flags \n\n";


echo "Test 3: setFlag2(FLAG_1 | FLAG_2); start: 4, expecting: 6 \n";
$flags = 4;
setFlag2(FLAG_1 | FLAG_2);
echo "value is $flags \n\n";


echo "Removing flags \n";

echo "Test 4: removeFlag(FLAG_3); start: 6, expecting: 6 \n";
removeFlag(FLAG_3);
echo "value is $flags \n\n";

echo "test 5: removeFlag2(FLAG_3); start: 6, expecting: 6 \n";
$flags = 6;
removeFlag2(FLAG_3);
echo "value is $flags \n\n";


echo "Test 6: removeFlag3(FLAG_3 | FLAG_2); start: 6, expecting: 2 \n";
removeFlag3(FLAG_3 | FLAG_2);
echo "value is $flags \n\n";

echo "Test 7: removeFlag4(FLAG_3 | FLAG_2); start: 6, expecting: 2 \n";
removeFlag4(FLAG_3 | FLAG_2);
echo "value is $flags \n\n";