<?php
 
$array = [
    'one' => 'a',
    'two' => [
        'default' => 'b',
            'three' => [
                'default' => 'c', 
                'four' => 'd'
            ],
    ],
];
$p = ['two', 'three', 'default'];
 
function getElementByPass($arr, $pass) {
        $result = $arr;
        foreach($pass as $index) {
            $result = $result[$index];
        }
        return $result;
    }
 
print_r(getElementByPass($array, $p));

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