__invoke for callable objects in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the object callable using __invoke.

PHP

<?php
class CallableClass {
    public function [1]() {
        echo "Called!";
    }
}
$obj = new CallableClass();
$obj();
?>

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

A__invoke

B__toString

C__construct

D__call

Attempts:

3 left

💡 Hint

Common Mistakes

Using __call instead of __invoke

Forgetting to define __invoke method

Trying to call the object without __invoke defined

The __invoke method allows an object to be called like a function.

2fill in blank

medium

Complete the code to return a string when the object is called.

PHP

<?php
class Greeter {
    public function [1]() {
        return "Hello!";
    }
}
$greet = new Greeter();
echo $greet();
?>

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

A__toString

B__destruct

C__callStatic

D__invoke

Attempts:

3 left

💡 Hint

Common Mistakes

Using __toString which is for string conversion

Trying to call the object without __invoke defined

The __invoke method can return values when the object is called like a function.

3fill in blank

hard

Fix the error in the code to make the object callable.

PHP

<?php
class Counter {
    private $count = 0;
    public function [1]() {
        $this->count++;
        return $this->count;
    }
}
$c = new Counter();
echo $c();
?>

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

A__get

B__call

C__invoke

D__set

Attempts:

3 left

💡 Hint

Common Mistakes

Using __call which is for undefined method calls

Not defining __invoke method

The __invoke method must be defined to allow the object to be called like a function.

4fill in blank

hard

Fill both blanks to create a callable object that multiplies a number by a factor.

PHP

<?php
class Multiplier {
    private $factor;
    public function __construct($factor) {
        $this->factor = [1];
    }
    public function [2]($number) {
        return $number * $this->factor;
    }
}
$mul = new Multiplier(5);
echo $mul(3);
?>

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

A$factor

B__call

C__invoke

D$this->factor

Attempts:

3 left

💡 Hint

Common Mistakes

Using __call instead of __invoke

Assigning wrong variable in constructor

Use $factor to assign the constructor argument, and __invoke to make the object callable.

5fill in blank

hard

Fill all three blanks to create a callable object that stores and returns a message.

PHP

<?php
class Messenger {
    private $message;
    public function __construct([1]) {
        $this->message = [2];
    }
    public function [3]() {
        return $this->message;
    }
}
$msg = new Messenger("Hi there!");
echo $msg();
?>

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

A$msg

B$message

C__invoke

D$this->message

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names in constructor

Not defining __invoke method

The constructor takes $message as argument and assigns it to $this->message. The __invoke method returns the message when the object is called.