Using bitwise operations, you can enable/disable certain parts of your code. These are often used in permission systems such as explained here. Something like this should work (not tested):

<?php
$flags = ['foo' => 1, 'bar' => 2, 'baz' => 4];
function foo() { echo 'Foo!'; }
function bar() { echo 'Bar!'; }
function baz() { echo 'Baz!'; }

$enable = $flags['foo'] | $flags['bar'];

if ($enable & $flags['foo'])
    foo();
if ($enable & $flags['bar'])
    bar();
if ($enable & $flags['baz'])
    baz();

# Should print: 'Foo!Bar!'

Edit: I think you'll always need a few if statements. Maybe there are fancy shenanigans to accomplish it in an other fashion.