PHP Bubble Sort O(n^2)

bubble-sort.php

<?php
function bubbleSort(array $array) {
    if ( empty( $array ) )
        return $array;

    $length = count($array);

    for ( $i = 0; $i < $length - 1; $i++ ) {
        $swapped = false;

        for ( $j = 0; $j < $length - $i - 1; $j++ ) {
            if ( $array[$j] > $array[$j + 1] ) {
                $temp = $array[$j];
                $array[$j] = $array[$j + 1];
                $array[$j + 1] = $temp;
                $swapped = true;
            }
        }

        if ( !$swapped )
            break;
    }

    return $array;
}