Define a set of constants to be used as flags for bitmasked options.

example.php

<?php

set_bitmask_flags([
    'FLAG_1',
    'FLAG_2',
    'FLAG_3',
    'FLAG_4',
    'FLAG_5',
]);

function example_flags($flags)
{
    if ($flags & FLAG_1) {
        echo "You passed flag 1!" . PHP_EOL;
    }
    if ($flags & FLAG_2) {
        echo "You passed flag 2!" . PHP_EOL;
    }
    if ($flags & FLAG_3) {
        echo "You passed flag 3!" . PHP_EOL;
    }
    if ($flags & FLAG_4) {
        echo "You passed flag 4!" . PHP_EOL;
    }
    if ($flags & FLAG_5) {
        echo "You passed flag 5!" . PHP_EOL;
    }
}

example_flags(FLAG_1 | FLAG_3 | FLAG_5);
// 'You passed flag 1!'
// 'You passed flag 3!'
// 'You passed flag 5!'

set_bitmask_flags.php

<?php

if (! function_exists('set_bitmask_flags')) {
    /**
     * Define a set of constants to be used as flags for bitmasked options.
     *
     * @param string[] $flags
     * @return void
     * @throws \InvalidArgumentException
     */
    function set_bitmask_flags(array $flags): void
    {
        $flags = array_values($flags);
        $index = 0;

        foreach ($flags as $flag) {
            $suffixZeroes = str_repeat('0', $index);
            $binary = "0b1{$suffixZeroes}";

            define($flag, bindec($binary));
            $index++;
        }
    }
}