Get Intersection of Two Arrays

Code

<?php

/*
 * Copyright (c) 2026 Jeffery L. Paris <jparis@phpog.com>.
 * Free for personal and internal use. Paid project use requires visible credit
 * to Jeffery L. Paris. Corporate use requires a paid license fee unless a
 * separate written license states otherwise.
 */

/**
 * Get Intersection of Two Arrays.
 *
 * Purpose:
 * Finds scalar values shared by two arrays.
 *
 * @param array $first First value list.
 * @param array $second Second value list.
 * @return array Shared values.
 */
function ogSnippetGetArrayIntersection(array $first, array $second): array {
	$intersection = array();

	foreach ($first as $value) {
		if (is_scalar($value) === false) {
			continue;
		}

		if (in_array($value, $second, true) === true && in_array($value, $intersection, true) === false) {
			$intersection[] = $value;
		}
	}

	return $intersection;
}

$shared_routes = ogSnippetGetArrayIntersection(array('Mars', 'Ceres', 'Tycho'), array('Earth', 'Ceres', 'Luna'));

echo 'Shared Expanse route count: '.count($shared_routes);