PHP 7 - iteratively populate multilevel array in callback

Question

I need to build complex multilevel array in callback only, one atomic update per call.

The reason for it: callback is called many times from iterative parser. Finally it should build deserialized PHP-array of binary format being parsed.

Here is runnable code:

const ACTION_VALUE = 1;
const ACTION_ENTER = 2;
const ACTION_LEAVE = 3;

function callback($action, $value, &$param)
{
   switch ($action) 
   {
    case ACTION_ENTER:
        $param['parent'][] = &$param['current'];
        $param['current'][] = [];

        end($param['current']);                
        $param['current'] = &$param['current'][key($param['current'])];
    break;

    case ACTION_LEAVE:
        unset($param['current']);
        $param['current'] = array_pop($param['parent']);
        end($param['current']);
    break;

    case ACTION_VALUE:
        $param['current'][] = $value;
    break;
   }
}

// prepare container
$arr = [];
$arr['data'] = [];
$arr['current'] = &$arr['data'];
$arr['parent'] = [];

// callback invocations
callback(ACTION_VALUE, 1, $arr);
callback(ACTION_VALUE, 2, $arr);
callback(ACTION_ENTER, 0, $arr);
callback(ACTION_VALUE, 10, $arr);
callback(ACTION_VALUE, 11, $arr);
callback(ACTION_LEAVE, 0, $arr);
callback(ACTION_VALUE, 3, $arr);
callback(ACTION_VALUE, 4, $arr);

// now see result
var_dump(json_encode($arr['data']));

Try it here

Above example prints:

[1,2,[10,11]], but should [1,2,[10,11],3,4].

Update: Multilevel means arbitrary arrays of random depth.

Update: The problem was with array_pop(), see below accepted answer for fixed version.

Could you try entering and leaving as a pointer? And on leave, add it to data and then point the pointer back to the main data? — Ice76
– Ice76, Commented Sep 28, 2018 at 0:38
If you mean, pass different "contexts" to callback? No, I can't since callback is called by parser, And parser knows nothing about how callback is used... and it just passthru &$param for all callback invocation, knows nothing about what &$param is. — ppmag
– ppmag, Commented Sep 28, 2018 at 0:49

Ice76 · Accepted Answer · 2018-09-28 00:58:13Z

2

You could do something like this, it definitely simplifies what you are trying to do. It just has different base array values, but it is similar enough, so I think it should work for your application of it.

Changes made: Restructured the array and used a addTo string as 'pointer'

const ACTION_VALUE = 1;
const ACTION_ENTER = 2;
const ACTION_LEAVE = 3;

// prepare container
$arr = [];
$arr['data'] = [];
$arr['addTo'] = 'data';
$arr['temp'] = [];

function callback($action, $value, &$param)
{
    switch ($action)
    {
        case ACTION_ENTER:
            $param['addTo'] = 'temp';
            break;

        case ACTION_LEAVE:
            $param['addTo'] = 'data';
            $param['data'][] = $param['temp'];
            $param['temp'] = [];
            break;

        case ACTION_VALUE:
            $param[$param['addTo']][] = $value;
            break;
    }
}



// callback invocations
callback(ACTION_VALUE, 1, $arr);
callback(ACTION_VALUE, 2, $arr);
callback(ACTION_ENTER, 0, $arr);
callback(ACTION_VALUE, 10, $arr);
callback(ACTION_VALUE, 11, $arr);
callback(ACTION_LEAVE, 0, $arr);
callback(ACTION_VALUE, 3, $arr);
callback(ACTION_VALUE, 4, $arr);

// now see result
var_dump(json_encode($arr['data']));

answered Sep 28, 2018 at 0:58

Ice76

1,1308 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

ppmag Over a year ago

Thank you, but unfortunately this approach do not work for 3+ nesting level. I can't build arbitrary arrays this way.

Karol Samborski · Accepted Answer · 2018-09-28 10:49:48Z

I think the problem is array_pop which doesn't return actual reference to the last element. This one works:

<?php

const ACTION_VALUE = 1;
const ACTION_ENTER = 2;
const ACTION_LEAVE = 3;

function callback($action, $value, &$param)
{
    switch ($action) {
        case ACTION_ENTER:
            $param['parent'][] = &$param['current'];
            $param['current'][] = [];

            end($param['current']);
            $param['current'] = &$param['current'][key($param['current'])];
            break;

        case ACTION_LEAVE:
            unset($param['current']);
            end($param['parent']);
            $param['current'] = &$param['parent'][key($param['parent'])];
            unset($param['parent'][key($param['parent'])]);
            end($param['current']);
            break;

        case ACTION_VALUE:
            $param['current'][] = $value;
            break;
    }
}

// prepare container
$arr = [];
$arr['data'] = [];
$arr['current'] = &$arr['data'];
$arr['parent'] = [];

// callback invocations
callback(ACTION_VALUE, 1, $arr);
callback(ACTION_VALUE, 2, $arr);
callback(ACTION_ENTER, 0, $arr);
callback(ACTION_VALUE, 10, $arr);
callback(ACTION_VALUE, 11, $arr);
callback(ACTION_ENTER, 0, $arr);
callback(ACTION_VALUE, 40, $arr);
callback(ACTION_VALUE, 41, $arr);
callback(ACTION_LEAVE, 0, $arr);
callback(ACTION_LEAVE, 0, $arr);
callback(ACTION_VALUE, 3, $arr);
callback(ACTION_VALUE, 4, $arr);

// now see result
var_dump(json_encode($arr['data']));

Collectives™ on Stack Overflow

PHP 7 - iteratively populate multilevel array in callback

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest