php 计算三维数组中某个一维数组的值

Array
(
    [0] => Array
        (
            [0] => Array
                (
                    [order_id] => 20200312190044958888
                )

            [1] => Array
                (
                    [order_id] => 20200312190044958999
                )

        )

    [1] => Array
        (
            [0] => Array
                (
                    [order_id] => 20200115162154147836
                )

        )

    [2] => Array
        (
        )

    [3] => Array
        (
        )

    [4] => Array
        (
        )

    [5] => Array
        (
        )

)

我现在想计算array里[0]里的order_id个数为2
[1]里的order_id个数为1
以此类推没有的是0. 我想计算order_id总个数。应该怎么做 谢谢

<?php 
    $arr1 = array(
                    0=>array(
                        0=>array('order_id'=>'20200312190044958888'),
                        1=>array('order_id'=>'20200312190044958999')
                    ),
                    1=>array(
                        0=>array('order_id'=>'20200115162154147836')
                        ),

                    2=>array(
                    ),

                    3=>array(
                    ),

                    4=>array(
                        0=>array('order_id'=>'20200115162154147839')
                    ),

                    5=>array(
                    )
                );
    // 计数
    $count = 0;
    // 最外层循环遍历数组$arr1
    $len = count($arr1);
    foreach($arr1 as $key1=>$value1)
    {
        $arr2=$value1;
        // 中间循环遍历数组$arr2
        foreach($arr2 as $key2=>$value2)
        {
            $arr3=$value2;
            // 最内层循环遍历数组$arr3
            foreach($arr3 as $key3=>$value3)
            {
                if($key3=='order_id')
                {
                    $count++;
                }
            }
        }
    }
    echo "数组\$arr1里面order_id个数为{$count}";

 ?>