How to implement class methods in array_map's callable

Question

I am trying to create a class to handle arrays but I can't seem to get array_map() to work in it.

$array = [1,2,3,4,5,6,7,8,9,10];
class test {
    public $values;

    public function adding($data) {
        $this->values = array_map($this->dash(), $data);
    }

    public function dash($item) {
        return '-' . $item . '-';
    }

}

var_dump($array);

$test = new test();
$test->adding($array);

// Expected: -1-,-2-,-3-,-4-... 
var_dump($test->values);

This outputs

array(10) { [0]=> int(1) [1]=> int(2) [2]=> int(3) [3]=> int(4) [4]=> int(5) [5]=> int(6) [6]=> int(7) [7]=> int(8) [8]=> int(9) [9]=> int(10) }

Warning: Missing argument 1 for test::dash(), called in [...]\arraytesting.php on line 11 and defined in [...]\arraytesting.php on line 15

Warning: array_map() expects parameter 1 to be a valid callback, function '--' not found or invalid function name in [...]\arraytesting.php on line 11 NULL

What am I doing wrong or does this function just not work inside classes?

score 169 · Accepted Answer · edited Jan 23 '23 at 08:25

169

You are specifying dash as the callback in the wrong way.

This does not work:

$this->classarray = array_map($this->dash(), $data);

This does:

$this->classarray = array_map([$this, 'dash'], $data);

Read about the different forms a callback may take here.

edited Jan 23 '23 at 08:25

Alexandre Huat

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16

answered Mar 24 '11 at 16:20

Jon

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Thank you for the quick replay. I got it working and thanks for you help. I was just wondering do you happen to have more article about callback and how to specify if correctly? – Justin Mar 24 '11 at 16:49
@Justin: Take a look here: http://stackoverflow.com/questions/48947/how-do-i-implement-a-callback-in-php – Jon Mar 24 '11 at 19:01
2

even statically works like array_map( @[ self, 'dash' ] ) – bortunac Jun 25 '16 at 22:53
How can you pass a parameter with the dash function? – Nielsapp May 10 '18 at 11:33
1

@Nielsapp you cannot directly, you must pass in a callable that will effectively bind the arguments that you want, e.g. `array_map(function($item) { return $this->dash($item, 'additional argument'); }, $data)` – Jon May 14 '18 at 09:49

score 16 · Answer 2 · answered Feb 24 '10 at 21:06

When using a class method as a callback for functions like array_map() and usort(), you have to send the callback as two-value array. The 2nd value is always the name of the method as a string. The 1st value is the context (class name or object)

// Static outside of class context
array_map( array( 'ClassName', 'methodName' ), $array );

// Static inside class context
array_map( array( __CLASS__, 'methodName' ), $array );

// Non-static outside of object context
array_map( array( $object, 'methodName' ), $array );

// Non-static inside of object context
array_map( array( $this, 'methodName' ), $array );

score 3 · Answer 3 · answered Mar 24 '11 at 16:21

3

array_map($this->dash(), $data) calls $this->dash() with 0 arguments and uses the return value as the callback function to apply to each member of the array. You want array_map(array($this,'dash'), $data) instead.

answered Mar 24 '11 at 16:21

Anomie

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score 2 · Answer 4 · answered Mar 24 '11 at 16:20

2

It must read

$this->classarray = array_map(array($this, 'dash'), $data);

The array-thing is the PHP callback for a object instance method. Callbacks to regular functions are defined as simple strings containing the function name ('functionName'), while static method calls are defined as array('ClassName, 'methodName') or as a string like that: 'ClassName::methodName' (this works as of PHP 5.2.3).

answered Mar 24 '11 at 16:20

Stefan Gehrig

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Thank you for you answer. I was very helpful do you have happen to know of any more articles about this subject? Thanks again, – Justin Mar 24 '11 at 17:21

score 1 · Answer 5 · answered Feb 24 '10 at 21:04

array_map takes a callback as its first parameter.

And a callback to a static method is written like this :

array('classname', 'methodname')

Which means that, in your specific case, you'd use :

array_map(array('stripSlashesRecursive', ''), $value);

For more informations about callbacks, see this section of the PHP manual : Pseudo-types and variables used in this documentation - callback.

score 1 · Answer 6 · answered Sep 16 '21 at 09:07

In case the class belongs to a different namespace, you need to use the complete namespaced class name. Below is an example using a CakePHP Utility class:

This will not work:

array_map(array('Inflector', 'humanize'), $some_array));

This will work:

array_map(array('Cake\Utility\Inflector', 'humanize'), $some_array));

score 0 · Answer 7 · answered Feb 24 '10 at 21:05

0

array_map( array('Sanitize', 'stripSlashesRecursive'), $value) ...

answered Feb 24 '10 at 21:05

aefxx

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score 0 · Answer 8 · answered Jun 09 '22 at 09:28

0

//Regular functions: array_map('MyFunction', $array);

//static functions in a class: array_map(array('MyClass', 'MyFunction'), $array);

//functions from an object: array_map(array($this, 'MyFunction'), $array);

//functions from an parent class array_map(array($this, 'parent::MyFunction'), $array);

answered Jun 09 '22 at 09:28

otto9due

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Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Ethan Jun 10 '22 at 01:16

score -1 · Answer 9 · answered Feb 15 '21 at 12:25

For multidimensional arrays (any arrays):

    $data = array_map('decode'), $data);

    function decode($data)
    {
        if (is_array($data)) {
            foreach ($data as &$value) {
                if (is_array($value)) {
                    $value = decode($value);
                } else {
                    $value = html_entity_decode($value);
                }
            }
        } else {
            $data = html_entity_decode($data);
        }
        return $data;
    }

For multidimensional arrays (any arrays) in Class:

$data = array_map(array($this,'decode'), $data);

private function decode($data)
{
    if (is_array($data)) {
        foreach ($data as &$value) {
            if (is_array($value)) {
                $value = $this->decode($value);
            } else {
                $value = html_entity_decode($value);
            }
        }
    } else {
        $data = html_entity_decode($data);
    }
    return $data;
}

How to implement class methods in array_map's callable

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