solution.php

<?php
function solution($X, $A) {
	foreach ($A as $key => $value) {
		$part1 = array_slice($A, 0, $key);
		$part2 = array_slice($A, $key, count($A) - 1);

		$arrayPart1Indexes = array();
		$arrayPart2Indexes = array();

		foreach ($part1 as $part1key => $part1Value) {
		    if ($part1Value === $X) {
		    	$arrayPart1Indexes[] = $part1key;
		    }
		}

		foreach ($part2 as $part2key => $part2Value) {
		    if ($part2Value !== $X) {
		    	$arrayPart2Indexes[] = $part2key;
		    }
		}

		if (count($arrayPart1Indexes) === count($arrayPart2Indexes)) {
		    return $key;
		}
	}

	return 0; //forget to put this on solution
}
?>