Sub-namespaces in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a sub-namespace in PHP?

A sub-namespace is a namespace nested inside another namespace, used to organize code into smaller, related groups.

beginner

How do you declare a sub-namespace in PHP?

Use backslashes to separate namespace levels, for example: namespace MyApp\\Utils\\Helpers; declares a sub-namespace Helpers inside Utils.

beginner

Why use sub-namespaces instead of one big namespace?

Sub-namespaces help keep code organized, avoid name conflicts, and make it easier to find related classes or functions.

beginner

How do you access a class in a sub-namespace?

Use the full namespace path with backslashes, for example: new \\MyApp\\Utils\\Helpers\\MyClass();.

intermediate

What happens if you omit the leading backslash when accessing a sub-namespace class?

PHP looks for the class relative to the current namespace, which may cause errors if the full path is not correct.

How do you declare a sub-namespace named 'Models' inside 'App'?

A namespace App\\Models;

B namespace App.Models;

C namespace App/Models;

D namespace App-Models;

In PHP, namespaces use backslashes (\\) to separate levels, so 'namespace App\\Models;' is correct.

What symbol separates sub-namespaces in PHP?

A \\

B /

C .

D -

PHP uses the backslash (\\) to separate namespaces and sub-namespaces.

If you are in namespace 'App\\Controllers', how do you create an object from 'App\\Models\\User'?

A new Models\\User();

B new User();

C new \\App\\Models\\User();

D new App\\Models\\User();

You need the full path with a leading backslash to access a class outside the current namespace.

Why are sub-namespaces useful?

A They make code run faster.

B They replace classes.

C They reduce file size.

D They organize code and avoid name conflicts.

Sub-namespaces help organize code and prevent name conflicts by grouping related code.

What happens if you forget the leading backslash when accessing a class in a different namespace?

A PHP automatically finds the class.

B PHP throws an error or looks in the wrong namespace.

C The class is loaded from global namespace.

D The code runs slower.

Without the leading backslash, PHP looks relative to the current namespace, which can cause errors.

Explain what sub-namespaces are and why they are useful in PHP.

Think about folders inside folders to keep things tidy.

Describe how to declare and use a class inside a sub-namespace in PHP.

Remember the backslash \\ is like a folder separator.