Sub-namespaces in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of accessing a class in a sub-namespace

What is the output of this PHP code?

PHP

<?php
namespace App\Models\User;
class Profile {
    public function getName() {
        return "User Profile";
    }
}

namespace App\Controllers;
use App\Models\User\Profile;
$profile = new Profile();
echo $profile->getName();

A Fatal error: Class 'App\Controllers\Profile' not found

B NULL

C App\Models\User\Profile

D User Profile

💡 Hint

Look at how the class is imported with 'use' and instantiated.

The 'use' statement imports the class from the sub-namespace. So creating a new Profile() calls the correct class and outputs 'User Profile'.

🧠 Conceptual

intermediate

Understanding sub-namespace declaration

Which of the following is the correct way to declare a sub-namespace in PHP?

A namespace App\Models\User;

B namespace App.Models.User;

C namespace App/Models/User;

D namespace App:Models:User;

💡 Hint

PHP namespaces use backslashes to separate levels.

PHP uses backslashes '\\' to separate namespace levels. So 'namespace App\\Models\\User;' is correct.

🔧 Debug

advanced

Identify the error in sub-namespace usage

What error will this PHP code produce?

PHP

<?php
namespace App\Models;
class User {}

namespace App\Models\User;
class Profile {}

$profile = new Profile();

A Fatal error: Uncaught Error: Class 'Profile' not found

B Fatal error: Uncaught Error: Class 'App\Models\User\Profile' not found

C No error, code runs fine

D Parse error: syntax error, unexpected token '$profile'

💡 Hint

Consider the current namespace when instantiating classes without 'use'.

The code tries to instantiate 'Profile' in the 'App\Models\User' namespace, so it looks for 'Profile' there. However, the instantiation is outside any namespace, so PHP looks for 'Profile' in the global namespace and fails. Without 'use' or fully qualified name, PHP looks for 'Profile' in the global namespace and fails.

📝 Syntax

advanced

Which code snippet correctly imports and uses a sub-namespace class?

Select the option that correctly imports and creates an object from a class in a sub-namespace.

A

<?php
use App:Models:User:Profile;
$profile = new Profile();

B

<?php
use App.Models.User.Profile;
$profile = new Profile();

C

<?php
use App\Models\User\Profile;
$profile = new Profile();

D

<?php
use App/Models/User/Profile;
$profile = new Profile();

💡 Hint

Remember the correct namespace separator in 'use' statements.

The 'use' statement must use backslashes '\\' to separate namespaces. Only option C uses the correct syntax.

🚀 Application

expert

Count classes in nested sub-namespaces

Given these PHP files with namespaces and classes, how many classes are declared in the 'App\Models' namespace and all its sub-namespaces combined? File 1:

A 4

B 3

C 2

D 1

💡 Hint

Count all classes declared in 'App\Models' and any namespace starting with it.

Classes in 'App\Models', 'App\Models\User', and 'App\Models\User\Settings' count. That is User, Profile, and Preferences = 3 classes. The class in 'App\Controllers' does not count.