<?php
$a = array('a'=>array('b'=>array('c'=>array('d'=>123,'s'=>4),'r'=>3),'q'=>2),'p'=>1);
$keys1 = array('a','b','c');
$keys2 = array('a','b');
$keys = $keys1; // set this as "search value"
$value = $a; // create a copy of original array. Maybe not needed?
Foreach($keys as $key){ // loop keys in search value
$value = $value[$key];
}
Var_dump($value); // dump the search return.