<?php
 
$array = [
	'a' => [
		[0, 1, 2, 3, 4, 5, 6, 7],
		[8, 9, 10, 11, 12, 13, 14, 15],
		[16, 17, 18, 19, 20, 21, 22, 23],
		[24, 25, 26, 27, 28, 29, 30, 31]
	],
	'b' => [
		[10, 11, 12, 13, 14, 15, 16, 17],
		[18, 19, 110, 111, 112, 113, 114, 115],
		[116, 117, 118, 119, 120, 121, 122, 123],
		[124, 125, 126, 127, 128, 129, 130, 131]
	]
];
 
foreach ($array as &$lvl1) {
	foreach ($lvl1 as &$lvl2) {
		foreach ($lvl2 as &$lvl3) {
			$lvl3 *= 2;
		}
		unset($lvl3);
		$lvl2 = implode(',', $lvl2);
	}
	unset($lvl2);
	$lvl1 = implode('::', $lvl1);
}
unset($lvl1);
 
$array = implode(';;;;', $array);
 
echo $array;

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