<?php
$xArray = $yArray = array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
$resultArray = array();
foreach($xArray as $x) {
	foreach($yArray as $y) {
		$result = $x + $y;
		$resultArray[$result] = $resultArray[$result] + 1;
	}
}
foreach ($resultArray as $key => $val) {
    if ($val == max($resultArray))
		echo $key;
}
?>

10