Unexpected behavior in recursive function

Question

The task is to remove arrays recursively that have error => 4 (i.e key with that value) with their keys, and then turn remained arrays into objects. The structure of incoming array might be different. Two examples of it are this ones:

// Example input #1
$ex_input_1 = array(
    'files' => array(
        0 => array(
            'name' => 'file.jpg',
            'size' => '244235',
            'tmp_name' => '/usr/tmp/24ffds.tmp',
            'error' => 0
        ),

        1 => array(
            'name' => '',
            'size' => '',
            'tmp_name' => '',
            'error' => 4
        )
    ),

    'cover' => array(
        'name' => '',
        'size' => '',
        'tmp_name' => '',
        'error' => 4
    ),

    'document' => array(
        'name' => 'file.doc',
        'size' => '244235',
        'tmp_name' => '/usr/tmp/24ffds.tmp',
        'error' => 0
    )
);

// Example input #2
$ex_input_2 = array(
    0 => array(
        'name' => 'file.jpg',
        'size' => '244235',
        'tmp_name' => '/usr/tmp/24ffds.tmp',
        'error' => 0
    ),

    1 => array(
        'name' => '',
        'size' => '',
        'tmp_name' => '',
        'error' => 4
    )
);

i.e an array that have name, size, tmp_name, error keys might be at any level down.

What I tried:

Tried to write a simple handler with two methods, where the first one is recursive handler and the second one is hydrator method. Here's it with relevant parts:

<?php

class FileInputParser
{
    /**
     * Recursively hydrate array entires skipping empty files
     * 
     * @param array $files
     * @return array
     */
    public function hydrateAll(array $files)
    {
        foreach ($files as $name => $file) {
            if (!is_array($file)) {
                continue;
            }

            foreach ($file as $key => $value) {
                if (is_array($value)) {
                    // Recursise call
                    $files[$name] = $this->hydrateAll($files[$name]);
                } else {
                    $target = $this->hydrateSingle($file);

                    // Here I'm EXPLICTLY asking not to push an array, which has error = 4
                    // But it pushes anyway!!
                    if ($target !== false) {
                        unset($files[$name]);
                    }
                }
            }
        }

        return $files;
    }

    /**
     * Hydrates a single file item
     * 
     * @param array $file
     * @return mixed
     */
    private function hydrateSingle(array $file)
    {
        $entity = new stdclass;
        $entity->name = $file['name'];
        $entity->tmp_name = $file['tmp_name'];
        $entity->error = $file['error'];
        $entity->size = $file['size'];

        if ($entity->error != 4) {
            return $entity;
        } else {
            // Returning false to indicate, that this one should not be pushed in output
            return false;
        }
    }
}

The problem

While at first glance it works, the problem is that, when I'm asking explicitly not to add an array that has error = 4 to output, but it continues to add!

You can run aforementioned code with input examples:

<?php

$parser = new FileInputParser();
$output = $parser->hydrateAll($ex_input_1);

echo '<pre>', print_r($output, true);

to see that it also returns unwanted arrays (i.e the ones that have error = 4).

The question

Why it continues to add arrays to output that have error = 4 ? if you have a better idea on handling this, I'd love to hear it.

Nick · Accepted Answer · 2019-01-20 06:53:48Z

Here's a recursive function that will do the filtering you want. When it reaches the bottom of the tree, it checks for error == 4 and if it is, returns an empty array, otherwise it returns the current array. At the next level down any empty values returned are removed by array_filter:

function array_filter_recursive($array) {
    if (isset($array['error'])) {
        // bottom of tree
        return $array['error'] == 4 ? array() : $array;
    }
    foreach ($array as $key => $value) {
        $array[$key] = array_filter_recursive($value);
    }
    // remove any empty values
    return array_filter($array);
}

Output from filtering your two input arrays:

Array ( 
    [files] => Array (
        [0] => Array ( 
            [name] => file.jpg
            [size] => 244235
            [tmp_name] => /usr/tmp/24ffds.tmp
            [error] => 0
        )
    )
    [document] => Array (
         [name] => file.doc
         [size] => 244235
         [tmp_name] => /usr/tmp/24ffds.tmp
         [error] => 0
    ) 
)

Array ( 
    [0] => Array (
        [name] => file.jpg
        [size] => 244235
        [tmp_name] => /usr/tmp/24ffds.tmp
        [error] => 0
    )
)

Demo on 3v4l.org

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