What is the default value for callback argument of array_filter function

Question

What is the default value for callback argument of array_filter function?

Let imagine we have array:

$input = [
    "Required field" => true
    "Please, enter a number" => false
];

Normally, I use array_filter without explicitly setting callback parameter, as array_filter( $input) and this function will return the following array:

$input = [
    "Required field" => true
];

But now I need to exactly set callback argument. So when I'm sending null as callback this functions return null and "non empty" value ("Required field" => true) is ignored, what would I not like.

Of course, I can call the function with own callback function like:

array_filter( $input, fn($item) => !empty($item) )

But I was hoping for more elegant way

Could you provide the input and desired output that you need for this case where simply calling array_filter without a callback is not sufficient for you? — El_Vanja
– El_Vanja, Commented Nov 22, 2020 at 13:32
Concerning your opening question, it is described in the docs you have linked yourself: If no callback is supplied, all empty entries of array will be removed. See empty() for how PHP defines empty in this case. — El_Vanja
– El_Vanja, Commented Nov 22, 2020 at 13:34
I just want to filter array from empty values with explicitly setting callback argument, but in more elegant way rather than setting own callback function. — Urmat Zhenaliev
– Urmat Zhenaliev, Commented Nov 22, 2020 at 13:47
The most elegant way really is not setting a callback. Why would you pass a callback that does exactly the same thing as the default? — El_Vanja
– El_Vanja, Commented Nov 22, 2020 at 13:50
I want to make array_filter_recursive function. Like in this example: stackoverflow.com/a/6795671/7265862. As you see, in the second function, there is $callback argument, which later will be passed to array_filter function. I don't want to make if else statement to check for null $callback argument. That's why I was asking community for elegant solution — Urmat Zhenaliev
– Urmat Zhenaliev, Commented Nov 22, 2020 at 14:03

jspit · Accepted Answer · 2020-11-22 15:21:47Z

1

If the source code of array_filter contains a second parameter, it is checked whether it is a real callable function. A string can also be passed. But even then it is checked whether this is a real function.

Variant 1: Define a function, then use its name

function isNotEmpty($val){
  return !empty($val);
}

$arr = [0,1,[],null,false,"a","",(object)[],-1];

$res = array_filter( $arr);
$res1 = array_filter( $arr, 'isNotEmpty');
    
var_dump($res === $res1); //bool(true)

Variant 2: Use the boolval function

$arr = [0,1,[],null,false,"a","",(object)[],-1];

$res = array_filter( $arr);
$res1 = array_filter( $arr, 'boolval');

var_dump($res === $res1);  //bool(true)

With the function boolvar () this also works apparently. However, the PHP manual says:

var The scalar value being converted to a bool.

But the examples for the boolval function also show an empty array as a value.

edited Nov 22, 2020 at 15:21

answered Nov 22, 2020 at 14:27

jspit

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2 Comments

Urmat Zhenaliev Over a year ago

Variant 2 is what I was searching for. Thank you!

Urmat Zhenaliev Over a year ago

Is there any link to the article about remark? I can't find it out

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