在php中循环从一个函数跳转到另一个函数的一些问题[关闭]

Question

i noticed a wired behavior of php when doing something like

the code below is trying to loop through all arrays in multiarray, and it it should return $n when it is not an array anymore.
basicly a counter for dimentions.

<?php 
//some random values multiarray
$arrays[1][2][3][5] = '1';
$arrays[1][2][3] = '1';
$arrays[1][2][3][4] = '1';
$arrays[3][6][3][1][5] = '2';

function second_func($array, $n)//adding $n then returning to 1st func
{
    $n++;
    first_func($array, $n);
}
function first_func($arrays, $n = 0)//checking if array then 2nd func, if not then return.
{
    if(is_array($arrays))
    { 
        foreach($arrays as $array)second_func($array, $n); 
    }else
    {
        echo $n; //working
        return $n; //not working
    };
}
$result[] = first_func($arrays);
print_r($result);//nothing here

or any similar actions, if i put file_put_contents inside 1st function, then the result will be different with each refresh, and the function cannot be returned just as it is, only echoing it works stable.

I remember i had a similar 2 function to delete cache files and ended up with clean hard drive, or a similar func to create file and i would have files in random folders over hd.

didnt check for similar quastions, cannot formulate the quastion right..

Answer 1

The problem with your code is that the first_func function does not always return a value, only when the argument is not an array. But since you call it initially with an array argument, that particular call will not return anything, and this explains the blank output you get. So, even when you call a function recursively (via second_func), you must still return something.

If I understand correctly, you want an output per "leaf" in the tree of nested arrays: for each leaf, its depth in the tree should be output.

Here is how you could do that:

function first_func($arrays, $n = 0) {
    if(is_array($arrays)) {
        $result = [];
        foreach($arrays as $array)
            $result = array_merge($result, first_func($array, $n+1));
    } else {
        $result = [$n];
    }
    return $result;
}

This will return an array of integers, where each integer represents the depth of a particular leaf in the data.

Note that I removed second_func, as it is quite trivial. Writing first_func($arrays, $n+1) is not less clear than second_func($array, $n). If however you want to keep second_func, then make sure to return a value:

function second_func($array, $n) {
    $n++;
    return first_func($array, $n);
}

For this data:

$arrays = [
    1 => [
        2 => [
            3 => "1   1"
        ]
    ],
    3 => [
        6 => [
            3 => [
                1 => [
                    5 => "2"
                ]
            ]
        ]
    ]
];

... the above code will return:

[3, 5]

Which can be formatted as 35 with:

echo implode("", first_func($arrays));