Binding closures to objects in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to bind the closure to the object and call it.

PHP

<?php
class Person {
    public $name = 'Alice';
}

$person = new Person();

$greet = function() {
    return "Hello, " . $this->name;
};

$boundGreet = $greet->[1]($person);
echo $boundGreet();
?>

Drag options to blanks, or click blank then click option'

Acall

BbindTo

Capply

Dattach

Attempts:

3 left

💡 Hint

Common Mistakes

Using call() instead of bindTo() causes errors because call() immediately invokes the closure.

Using apply() or attach() which do not exist in PHP for closures.

The bindTo method binds a closure to an object, allowing it to use the object's properties via $this.

2fill in blank

medium

Complete the code to bind the closure to the object and specify the class scope.

PHP

<?php
class User {
    private $role = 'admin';
    public function getRoleClosure() {
        return function() {
            return $this->role;
        }->[1]($this, __CLASS__);
    }
}

$user = new User();
$closure = $user->getRoleClosure();
echo $closure();
?>

Drag options to blanks, or click blank then click option'

AbindTo

Bcall

Capply

Dattach

Attempts:

3 left

💡 Hint

Common Mistakes

Not passing the class scope causes private properties to be inaccessible.

Using call() which immediately invokes the closure instead of binding.

bindTo can take a second argument to specify the class scope, allowing access to private properties.

3fill in blank

hard

Fix the error by completing the code to bind the closure to the object correctly.

PHP

<?php
class Product {
    public $price = 100;
}

$product = new Product();

$discount = function($amount) {
    return $this->price - $amount;
};

$boundDiscount = $discount->[1]($product);
echo $boundDiscount(20);
?>

Drag options to blanks, or click blank then click option'

Aapply

Bcall

Cattach

DbindTo

Attempts:

3 left

💡 Hint

Common Mistakes

Using call() which immediately invokes the closure and does not return a bound closure.

Using non-existent methods like apply() or attach().

bindTo binds the closure to the object so $this refers to the object inside the closure.

4fill in blank

hard

Fill both blanks to create a closure bound to the object and call it with an argument.

PHP

<?php
class Calculator {
    public $factor = 2;
}

$calc = new Calculator();

$multiply = function($num) {
    return $num * $this->factor;
};

$boundMultiply = $multiply->[1]([2]);
echo $boundMultiply(5);
?>

Drag options to blanks, or click blank then click option'

AbindTo

Bcall

C$calc

D$multiply

Attempts:

3 left

💡 Hint

Common Mistakes

Using call instead of bindTo returns the result immediately, not a bound closure.

Passing the closure itself instead of the object to bind.

bindTo binds the closure to the object $calc so $this inside the closure refers to $calc.

5fill in blank

hard

Fill all three blanks to bind the closure to the object with class scope and call it with an argument.

PHP

<?php
class Logger {
    private $prefix = '[LOG]';
}

$logger = new Logger();

$logMessage = function($msg) {
    return $this->prefix . ' ' . $msg;
};

$boundLog = $logMessage->[1]([2], [3]);
echo $boundLog('System started');
?>

Drag options to blanks, or click blank then click option'

AbindTo

B$logger

C__CLASS__

Dcall

Attempts:

3 left

💡 Hint

Common Mistakes

Using call instead of bindTo causes immediate invocation, not binding.

Not passing the class scope causes private properties to be inaccessible.

bindTo binds the closure to the object $logger with the class scope __CLASS__ to access private properties.