<?php
function a ($option) {
    b($option['bla']);
    c($option);
    var_dump($option);
}
function b (&$string) {
    $string = 'changed';
}
function c ($option) {
    switch ($option['bla']) {
    case 'changed':
        $copy = $option;
        $copy['bla'] = 'copy';
        break;
    }
}
a(array('bla' => 'false'));
?>