Custom callback with parameter to be called by array_filter()

Question

I got this multiple array named $files[], which consists of keys and values as below:

[
    [
        'name' => 'index1.php',
        'path' => 'http://localhost/php/gettingstarted/',
        'number' => 1,
    ],
    [
        'name' => 'index10.php',
        'path' => 'http://localhost/php/gettingstarted/',
        'number' => 2,
    ],
    [
        'name' => 'index11.php',
        'path' => 'http://localhost/php/gettingstarted/',
        'number' => 3,
    ],
]

I use this code to create a new array consist of 'name' keys only. But it failed

array_filter($files, "is_inarr_key('name')");

function is_inarr_key($array, $key)
{
    //TODO : remove every array except those who got the same $key
}

and I get this error:

array_filter() [function.array-filter]: The second argument, 'is_inarr_key('name')', should be a valid callback in C:\xampp\htdocs\php\gettingstarted\index.php on line 15

So my questions are:

Is it possible to make the call-back function on array_filter receive parameter?
What is the general rule of thumb on how to use callback in any PHP built-in function?

This question is Unclear about the actual required filtering logic. Can we have a minimal reproducible example please? Are you retaining rows which have a key called name or are you filtering rows which contain a specific value in the name column or are you wanting to isolate the values in the name column as a new array? That I use this code to create a new array consist of 'name' keys only. sentence makes me believe it is the third one. In which case, you don't need array_filter(), you want array_column(). This question may be an XY Problem. — mickmackusa
– mickmackusa ♦, Commented Dec 15, 2023 at 10:48

kennytm · Accepted Answer · 2016-06-21 03:41:33Z

44

You can create a closure on PHP ≥5.3.

array_filter($files, function($array) use ($key) {
  return is_inarr_key($array, $key); 
} );

If you are stuck with PHP <5.3, …

You can make $key a global variable.

function is_inarr_with_global_key($array) {
   global $key;
   ....
}

You can create a class

class KeyFilter {
  function KeyFilter($key) { $this->key = $key; }
  function is_inarr_key($array) { ... }
}
...
array_filter($files, array(new KeyFilter('name'), 'is_inarr_key'));

You can create 3 different functions

array_filter($files, 'is_inarr_name');
array_filter($files, 'is_inarr_path');
array_filter($files, 'is_inarr_number');

You can write your own array_filter

function my_array_filter($files, $key) {
  ...
}

edited Jun 21, 2016 at 3:41

answered Mar 27, 2010 at 15:15

kennytm

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2 Comments

justjoe Over a year ago

i haven't try it. but this solution's brilyan. if i convert my code work with closure or class, i will able to work with more keys AND create ONLY one fun ction : is_inarr_key()

Mark Amery Over a year ago

+1, but if it were my answer I would list the closure-based solution first and recommend it over the alternatives. It's the simplest and shortest of the possibilities by far.

codaddict · Accepted Answer · 2010-03-27 15:24:26Z

2

You can make use of the array_walk function as:

$arr = array(
        array("name" => "Jack", "id" => 1),
        array("name" => "Rose", "id" => 2),
    );

$result = array(); // initialize result array.
array_walk($arr, "filter"); // iterate over the array calling filter fun for each value.
// $result will now have elements "Jack" and "Rose"

function filter($a) {

    global $result; // to access the global result array.

    $result[] = $a['name']; // for each array passed, save the value for the key 'name' in the result array.
}

answered Mar 27, 2010 at 15:24

codaddict

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Comments

Anthony Forloney · Accepted Answer · 2010-03-27 15:13:38Z

1

I am unaware if you can supply the callback function with parameters, but as a suggestion, you could define a callback function for array_filter

array_filter($files, "is_inarr_key");

And to get the name of the array, just loop over the $file[] and retrieve the name. Then, having the name you can go on with your logic.

HTH.

answered Mar 27, 2010 at 15:13

Anthony Forloney

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Comments

Jacob Singh · Accepted Answer · 2012-11-05 11:57:34Z

1

You can use create_function() in 5.2.x

$y = 5;
$func = 'return $x > ' . $y . ';';
$f = create_function('$x', $func);
$numbers = range(0, 10);
$result = array_filter($numbers, $f);
print_r($result);

which outputs

Array ( [6] => 6 [7] => 7 [8] => 8 [9] => 9 [10] => 10 )

edited Nov 5, 2012 at 11:57

user577537

answered Feb 8, 2011 at 15:38

Jacob Singh

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Comments

Community · Accepted Answer · 2017-05-23 12:06:49Z

1

thanks KennyTM for keyfilter class great tip. For those who care and don't know how to do it, this a working detailed example. I slightly improved using a regexp pattern.

$files[]= {code above};

class KeyFilter {
    function KeyFilter($attr,$pattern)
    {
        $this->attr=$attr;
        $this->pattern=$pattern;
    }
    function is_inarr_key($t)
    {
        return preg_match($this->pattern,$t[$this->attr]);;
    }
}


$t=array_filter($items, array(new KeyFilter("path","~\d{2}\.php~i"), 'is_inarr_key'));
print_r($t);
print_r($o->key);

output:

[1] => Array
(
    [name] => index**10**.php
    [path] => http://localhost/php/gettingstarted/
    [number] => 2
)

[2] => Array
(
    [name] => index**11**.php
    [path] => http://localhost/php/gettingstarted/
    [number] => 3
)

edited May 23, 2017 at 12:06

CommunityBot

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answered Nov 21, 2012 at 18:23

skyrail

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