代码实现：

/**
*	插入排序
*	在要排序的一组数中，假设前面的数已经是排好顺序的，现在要把第n个数插到前面的有序数中，使得这n个数也是排好顺序的。如此反复循环，直到全部排好顺序。
*/
function insertSort($arr) {
    $len=count($arr); 
    //这个元素 就是从第二个元素开始，到最后一个元素都是这个需要排序的元素
    for($i=1;$i<$len; $i++) {
        $tmp = $arr[$i];
        //内层循环控制，比较并插入
        for($j=$i-1;$j>=0;$j--) {
            if($tmp < $arr[$j]) {
                //发现插入的元素要小，交换位置，将后边的元素与前面的元素互换
                $arr[$j+1] = $arr[$j];
                $arr[$j] = $tmp;
            } else {
                //如果碰到不需要移动的元素，由于是已经排序好是数组，则前面的就不需要再次比较了。
                break;
            }
        }
    }
    return $arr;
}
//测试
$arr = [5,2,1,1,3,1,4];
// $arr = [5,2,0,0];
$end = insertSort($arr);
echo "<pre>";
print_r($end);

过程分析：

第1轮
Array ( [0] => 2 [1] => 5 [2] => 1 [3] => 1 [4] => 3 [5] => 1 [6] => 4 )
第2轮
Array ( [0] => 2 [1] => 1 [2] => 5 [3] => 1 [4] => 3 [5] => 1 [6] => 4 )
Array ( [0] => 1 [1] => 2 [2] => 5 [3] => 1 [4] => 3 [5] => 1 [6] => 4 )
第3轮
Array ( [0] => 1 [1] => 2 [2] => 1 [3] => 5 [4] => 3 [5] => 1 [6] => 4 )
Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 5 [4] => 3 [5] => 1 [6] => 4 )
第4轮
Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 3 [4] => 5 [5] => 1 [6] => 4 )
第5轮
Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 3 [4] => 1 [5] => 5 [6] => 4 )
Array ( [0] => 1 [1] => 1 [2] => 2 [3] => 1 [4] => 3 [5] => 5 [6] => 4 )
Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 5 [6] => 4 )
第6轮
Array ( [0] => 1 [1] => 1 [2] => 1 [3] => 2 [4] => 3 [5] => 4 [6] => 5 )