How to implement class methods in array_map's callable [duplicate]

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?

Alexandre Huat · Accepted Answer · 2023-01-23 08:25:02Z

173

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, 2023 at 8:25

Alexandre Huat

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answered Mar 24, 2011 at 16:20

Jon

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6 Comments

Justin Over a year ago

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?

Jon Over a year ago

@Justin: Take a look here: stackoverflow.com/questions/48947/…

bortunac Over a year ago

even statically works like array_map( @[ self, 'dash' ] )

Nielsapp Over a year ago

How can you pass a parameter with the dash function?

Jon Over a year ago

@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)

|

Peter Bailey · Accepted Answer · 2010-02-24 21:06:58Z

17

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 );

answered Feb 24, 2010 at 21:06

Peter Bailey

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Comments

Anomie · Accepted Answer · 2011-03-24 16:21:45Z

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, 2011 at 16:21

Anomie

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Comments

Stefan Gehrig · Accepted Answer · 2011-03-24 16:20:57Z

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, 2011 at 16:20

Stefan Gehrig

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1 Comment

Justin Over a year ago

Thank you for you answer. I was very helpful do you have happen to know of any more articles about this subject? Thanks again,

Pascal MARTIN · Accepted Answer · 2010-02-24 21:04:09Z

1

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.

answered Feb 24, 2010 at 21:04

Pascal MARTIN

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Comments

Aris · Accepted Answer · 2021-09-16 09:07:33Z

1

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));

answered Sep 16, 2021 at 9:07

Aris

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Comments

aefxx · Accepted Answer · 2010-02-24 21:05:16Z

0

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

answered Feb 24, 2010 at 21:05

aefxx

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Comments

otto9due · Accepted Answer · 2022-06-09 09:28:23Z

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 9, 2022 at 9:28

otto9due

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1 Comment

Ethan Over a year ago

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