PHP Insertion Sort O(n^2)

insertion-sort.php

<?php
// O(n^2)
function insertionSort( array $array ) {
    $length = count($array);
    for ( $i = 1; $i < $length; $i++ ) {
        $j = $i;
        while ( $j > 0 && $array[$j] < $array[$j-1] ) {
            $temp = $array[$j];
            $array[$j] = $array[$j-1];
            $array[$j-1] = $temp;
            $j--;
        }
    }
    return $array;
}