Filter recursive array and only remove NULL value

Question

I want to remove all null or blank value but not false and 0 value from recursive array.

function isNotNull($val) {
    if(is_array($val)) {
        $ret = array_filter($val, 'isNotNull');
        return $ret;
    } else {
        return (!is_null($val) && $val !== '');
   }

}

$arr = array_filter($arr, 'isNotNull');

Input:

$arr = array(
"stringKey" => "Abc",
"boolKey" => false,
"zeroKey" => 0,
"blankKey" => '',
"newArr" => array(
    "stringKey2"=>"Abc2", 
    "boolKey2"=>false, 
    "zeroKey2" => 0, 
    "blankKey2"=>"", 
    "blankArr" => array()
    )
);

This give output:

Array
(
    [stringKey] => Abc
    [boolKey] => 
    [zeroKey] => 0
    [newArr] => Array
        (
            [stringKey2] => Abc2
            [boolKey2] => 
            [zeroKey2] => 0
            [blankKey2] => 
            [blankArr] => Array
                (
                )
        )
)

But i want to bellow output:

 Array
(
    [stringKey] => Abc
    [boolKey] => 
    [zeroKey] => 0
    [newArr] => Array
        (
            [stringKey2] => Abc2
            [boolKey2] => 
            [zeroKey2] => 0
        )
)

I used array_filter with callback function but it only filter simple array not multidimensional array. I don't want to use loop.

you call callback function from inside of callback function. why? — diavolic
– diavolic, Commented Apr 18, 2017 at 7:45
you use is_null() function, but it works only when you set variable to NULL. To get needed result use empty() — diavolic
– diavolic, Commented Apr 18, 2017 at 9:20
empty() remove false or 0 values but i don't want to remove 0 or false value — Krishna Kumar Yadav
– Krishna Kumar Yadav, Commented Apr 18, 2017 at 12:10
Relevant: Recursively filter a multidimensional array and collect elements with a minimum string length and How to remove empty entries of an array recursively? — mickmackusa
– mickmackusa ♦, Commented Oct 29, 2023 at 21:52

Philipp · Accepted Answer · 2017-04-18 12:33:52Z

7

You could combine array_map and array_filter in an recursive called function. Something like this could work for you.

function filterNotNull($array) {
    $array = array_map(function($item) {
        return is_array($item) ? filterNotNull($item) : $item;
    }, $array);
    return array_filter($array, function($item) {
        return $item !== "" && $item !== null && (!is_array($item) || count($item) > 0);
    });
}

edited Apr 18, 2017 at 12:33

answered Apr 18, 2017 at 7:49

Philipp

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Comments

sevavietl · Accepted Answer · 2017-04-20 07:00:17Z

2

Don't need to reinvent recursion yourself. You can use RecursiveCallbackFilterIterator:

$iterator = new RecursiveIteratorIterator(
    new RecursiveCallbackFilterIterator(
        new RecursiveArrayIterator($arr),
        function ($value) {
            return $value !== null && $value !== '';
        }
    )
);

$result = iterator_to_array($iterator);

Here is working demo.

You should try to use as much stuff from Standard PHP Library (SPL) as you can.

UPDATE: As it is stated in the comments, the solution with iterator not actually suits for this purpose.

In the comments to the array_walk_recursive function you can find the implementation of walk_recursive_remove function:

function walk_recursive_remove (array $array, callable $callback) { 
    foreach ($array as $k => $v) { 
        if (is_array($v)) { 
            $array[$k] = walk_recursive_remove($v, $callback); 
        } else { 
            if ($callback($v, $k)) { 
                unset($array[$k]); 
            } 
        } 
    } 

    return $array; 
}

This generalized version of recursion function takes criteria in the form of callback. Having this function you can remove empty elements like this:

$result = walk_recursive_remove($arr, function ($value) {
    return $value === null || $value === '';
});

Here is working demo.

edited Apr 20, 2017 at 7:00

answered Apr 18, 2017 at 9:47

sevavietl

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3 Comments

sevavietl Over a year ago

@Philipp, yes, my bad. I have updated my answer. Thank you for pointing this.

Døner M. Over a year ago

Nice solution. Is there a way to let it remove sub-arrays with a certain key instead of a value?

sevavietl Over a year ago

@DønerM., thank you. $key is passed as a second parameter to the callback. So you can use it to match criteria.

Sahil Gulati · Accepted Answer · 2017-04-18 14:18:02Z

Here you require filtering of an array for empty string. In this code below you can add no of checks to filter it recursively. Hope it will work fine.

Try this code snippet here

<?php

ini_set('display_errors', 1);
//Using more complexed sample array for filter it.
$arr = array(
    "stringKey" => "Abc",
    "boolKey" => false,
    "zeroKey" => 0,
    "blankKey" => '',
    "newArr" => array(
        "stringKey2" => "Abc2",
        "boolKey2" => false,
        "zeroKey2" => 0,
        "blankKey2" => "",
        "blankArr" => array(
            "blankString"=>"",
            "zeroKey"=>0,
            "blankArr3"=>array()
        )
    )
);

$result=recursiveFilter($arr);
print_r($result);


function recursiveFilter($value)
{
    foreach ($value as $key => $value1)
    {
        if ($value1 === "")  unset($value[$key]);//you can add no. of conditions here.
        else if (is_array($value1)) $value[$key] = recursiveFilter($value1);
    }
    return $value;
}

Output:

Array
(
    [stringKey] => Abc
    [boolKey] => 
    [zeroKey] => 0
    [newArr] => Array
        (
            [stringKey2] => Abc2
            [boolKey2] => 
            [zeroKey2] => 0
            [blankArr] => Array
                (
                    [zeroKey] => 0
                    [blankArr3] => Array
                        (
                        )

                )

        )

)

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