<?php

$a1 = [
	0 => 2,
	1 => 1,
	2 => 8,
	3 => 10,
	4 => 11,
	12 => 9,
];
$a2 = [
	0 => 9,
	1 => 8,
	2 => 1,
	3 => 11,
	4 => 10,
	5 => 2,
];
print_r(array_combine(array_flip($a1), $a2));