array_walk_recursive with array?

Question

I have a menu array, it's a multidimensional array, and I want to do some thing with every single item, so I tried array_walk_recursive. Here is the menu:

$menu = array(
    array(
        'name'=>'a',
        'url'=>'b',
    ),
    array(
        'name'=>'c',
        'url'=>'d',
        'children'=>array(
            array(
                'name'=>'e',
                'url'=>'f'
            )
        )
    )
);

But array_walk_recursive only let me handle every single element, but not array.

array_walk_recursive($menu, function(&$item){
    var_dump($item);//return a;b;c;d;e;f;g
});

What I want is like this:

array_walk_recursive_with_array($menu, function(&$item){
    var_dump($item);//return array('name'=>'a','url'=>'b');a;b;array('name'=>'c',...);c;d;...
    if(is_array($item) && isset($item['name'])){
        // I want to do something with the item.
    }
})

Is there any PHP native function implementation?

array_walk_recursive is to modify array. how would you want your $menu to be after array_walk_recursive is executed. — bansi
– bansi, Commented Jul 3, 2014 at 12:36

danronmoon · Accepted Answer · 2018-04-18 14:59:48Z

4

according to the array_walk_recursive documentation, you can't get the inner array key. One way to perform your need is to use array_walk and creating your own recursivity.

function HandleArray(&$value){
    if(is_array($value)){
        //Do something with all array
        array_walk($value,'HandleArray');
    }
    else{
       //do something with your scalar value
    }
}
array_walk(array($your_array),'HandleArray');

edited Apr 18, 2018 at 14:59

danronmoon

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answered Jul 3, 2014 at 12:46

artragis

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2 Comments

mach128x Over a year ago

Right. As per the PHP doc : "Any key that holds an array will not be passed to the function." Why that is, is beyond me. Seems counter-intuitive for a function named "recursive".

sneeuwitje Over a year ago

@mach128x Walking array-keys that hold an array recursively will blow up when arrays inside are self-referenced. You would at least need a maxDepth parameter to stop infinite recursion before it does. The HandleArray() example above will also need a protection from infinite recursion if the input array is from an unknown source.

mickmackusa · Accepted Answer · 2020-03-07 05:03:58Z

You want to recursively search your array and perform some action every time your encounter an array that contains a key of name.

To demonstrate, here is a sample array that has a non-qualifying subarray ($array[1]) and three qualifying subarrays ($array[0], $array[2], and $array[2]['children']).

$array = [
    [
        'name' => 'a',
        'url' => 'b',
    ],
    [
        'no-name' => 'foo',
    ],
    [
        'name' => 'c',
        'url' => 'd',
        'children' => [
            [
                'name' => 'e',
                'url' => 'f'
            ]
        ]
    ]
];

To process the array, recursively access each node in the data structure. When an array is encountered, use isset() (or array_key_exists() if you need to respect potentially null values) to check if the array qualifies for your desired action.

Below is a script that will execute the recursive technique with the qualifying rules and add a new element whenever the rules are satsified. & is used in two places to indicate that a variable should be "modified by reference" -- this makes data mutation available outside of the scope of the custom function call.

Code: (Demo)

function recurseAll(&$node) {
    if (is_array($node)) {
        if (isset($node['name'])) {
            // do something with the qualifying array...
            $node[] = 'push a new element into array level';
        }
        foreach ($node as &$childNode) {
            recurseAll($childNode);
        }
    }
}

recurseAll($array);
var_export($array);

Output:

array (
  0 => 
  array (
    'name' => 'a',
    'url' => 'b',
    0 => 'push a new element into array level',      // added element to $array[0]
  ),
  1 => 
  array (                                            // didn't qualify
    'no-name' => 'foo',
  ),
  2 => 
  array (
    'name' => 'c',
    'url' => 'd',
    'children' => 
    array (
      0 => 
      array (
        'name' => 'e',
        'url' => 'f',
        0 => 'push a new element into array level', // added element to $array[2]['children']
      ),
    ),
    0 => 'push a new element into array level',     // added element to $array[2]
  ),
)

sneeuwitje · Accepted Answer · 2021-06-22 02:51:58Z

An infinite recursion safe-guard in @artragis example using array_walk() seems necessary. An ArrayHelper class example to reduce a given array to the array-values of a given array-key:

class ArrayHelper {
    /**
     * arrayFlattenToKeyValues - Like finding keys with array_walk_recursive()
     *   without the restriction "Any key that holds an array will not be passed to the function"
     * @see https://www.php.net/manual/en/function.array-walk-recursive.php#refsect1-function.array-walk-recursive-examples
     * @param array $deepArray
     * @param string $fromKey
     * @param int $maxDepth default = 10
     * @param array $accumulator default = []
     *
     * @return array
     */
    public static function arrayFlattenToKeyValues(
        array $deepArray,
        string $fromKey,
        int $maxDepth = 10,
        array $accumulator = []
    ): array {
        array_walk($deepArray, function ($value, $key) use (&$accumulator, $fromKey, $maxDepth) {
            if ($key === $fromKey) {
                $accumulator[] = $value;
            }
            if ($maxDepth > 0 && is_array($value)) {
                $accumulator = self::arrayFlattenToKeyValues($value, $fromKey, $maxDepth - 1, $accumulator);
            }
        });

        return $accumulator;
    }
}

This can probably be improved, simplified or done differently; please do!

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