PHP object closure error when assigning an anonymous function

Question

I received the following error :

Closure Object ( [this] => test1 Object ( ) [parameter] => Array ( [$handler] => ) )

I have no idea what it means, I am trying out new things with php. My purpose is to call an anonymous function to execute a list of commands on the fly, for the purpose of learning php call backs and closures i created 3 classes.

test1, test2 extends hand

<?php

// test1.php

class test1 
{
    public function __construct() {
    }    

    function dataTable() {
        test2::table("food", function(hand $handler){
            $handler->put("cookies");
        });
    }

}

// test2.php

class test2 extends hand
{
    public function __construct() {
        echo $this->info;
    }

    static function table($s, $b) {
        echo "called from Test2, Table 1st parameter ";
        echo $s ." <br><br> &nbsp";
        echo "called from Tes2, table 2nd parameter ";
        print_r($b);
        echo "---end";
    }
}

// hand.php

class hand
{
    protected $info;

    public function __construct() {
        print_r($this->info);
    }

    function put($b) {
        $this->info = $b;
    }
}

I want to retrieve the result entered here $handler->put("cookies");

from within the hand class and test2 class, the first parameter works as expected but i received an unfamiliar php error with the second parameter.

Please help, what am i doing wrong or aren't doing? i am trying to understand the callback and closures

Hi Darragh, thanks abunch, it was quite helpful, i have now passed in an argument of type hand but returns null, any suggestions? — Martin
– Martin, Commented May 28, 2015 at 14:25

Darragh Enright · Accepted Answer · 2015-05-28 13:49:23Z

Okay, I am going to extend my comment into an answer.

First of all, you are not receiving an error. It is the output from the line print_r($b);.

You have successfully passed the anonymous function to test2::table() as the second argument $b. However you have not executed it. To do so you need to call it. You execute an anonymous function (with no arguments) like so:

$b();

However, in your code $b requires a single argument of type hand, otherwise you will receive a Catchable fatal error and your code will fail at that point.

Since the test2 class extends from hand I am guessing that you intend to call the anonymous function with the current object context, like so:

$b($this);

However this will not work, because the test2::table() method is static. Therefore, it does not have specific object context, which means $this is not available.

The following is a simplified example of what I think you are trying to achieve more or less:

<?php

class Hand
{
    protected $info;

    function put($b)
    {
        $this->info = $b;
    }
}

class Test2 extends Hand
{
    function table($s, $b)
    {
        var_dump($this->info); // outputs null
        $b($this);             // execute the anonymous function
        var_dump($this->info); // outputs 'cookies'
    }
}

class Test1
{
    function dataTable()
    {
        $test2 = new Test2();
        $test2->table('food', function(Hand $handler){
            $handler->put('cookies');
        });
    }
}

$test1 = new Test1();
$test1->dataTable();

Note, that the table method is no longer static. Now you can pass it the executing object's context. Since all the code does is assign the value "cookies" to property Hand::$info; I've also added some var_dump calls to show that the property is null before executing the anonymous function and set to 'cookies' afterwards.

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