array_moonwalk test

array_moonwalk.php

<?php

/**
 * Moonwalk an array.
 *
 * Deduplicates multidimensional array by flattening it while preserving
 * the deepest depth and flipping it inside out. Array values become the
 * keys and the new values contain the depths.
 *
 * @since Hyperdrive 1.0.0
 * @param array $array A multidimensional array of variable depth.
 * @param array $accumulator A reference identifier for a stored result.
 * @param integer [$depth = 1] Starting depth for array search.
 * @param boolean [$recursing = false] True while doing a moonwalk.
 * @return A flattened, deduplicated array with leaf node values as keys
 *     and deepest depth of any given leaf as the value.
 */
function array_moonwalk( $array, &$accumulator, &$depth = 1, $recursing = false ) {
	array_walk( $array, function ( $element ) use ( &$accumulator, &$depth, $recursing ) {
		is_array( $element )
			? ++$depth && array_moonwalk( $element, $accumulator, $depth, true )
			: $accumulator[ $element ] = $depth;
	});
	$recursing && --$depth;
}


$antiparticles = [
	'one',
	'two',
	'three',
	[
		'two',
		'four',
	],
	'four',
];

$injectors = [];

array_moonwalk( $antiparticles, $injectors );

var_dump( $injectors );

results.txt

array(4) {
  ["one"]=>
  int(1)
  ["two"]=>
  int(2)
  ["three"]=>
  int(1)
  ["four"]=>
  int(1)
}

"four" should have a depth of 2 not 1

Updated version: https://gist.github.com/matt-h/36965782f0390b938ad8f17f7aec17ef