PHP Namespace and the Use Statement: Understanding the Basics

In PHP, namespaces provide a means of organizing and grouping related classes, interfaces, and traits. Typically, each namespace is associated with a specific project or library. To declare a namespace, use the following syntax:

namespace Shape;

This line indicates that all subsequent classes and methods will reside within the Shape namespace.

Regarding the specific issue encountered, it's crucial to note that the use statement serves a different purpose than the include statement. The include statement simply loads the contents of the specified file into the current scope, making its contents available. In contrast, the use statement allows you to reference classes or interfaces from other namespaces or the global namespace.

In your case, the use statement you attempted in the Circle.php file is incorrect. The proper syntax for aliasing Shape in your Circle class using the use operator would be as follows:

use Shape\Shape;

By using this statement, you instruct PHP to resolve Shape within the Shape namespace. Since both the Circle and Shape classes are defined within the same namespace, there is no need to specify the namespace prefix in the extends statement.

Finally, if you prefer not to use the use statement, you can explicitly specify the fully qualified namespace of the Shape class in the extends statement:

class Circle extends \Shape\Shape implements ShapeInterface {
    ...
}

This approach explicitly specifies the Shape class's namespace, avoiding the need for the use statement.