- print_r: documentation ( source)
- array_filter: documentation ( source)
- in_array: documentation ( source)
<?php
$config = ["a" => "green", "b" => "red", "d" => "blue"];
$allow = ["a","b","c"];
$result = \array_filter($config, function ($item) use ($allow) {
return \in_array($item, $allow, true);
}, \ARRAY_FILTER_USE_KEY);
print_r($result);