Using namespaces

An aspect that is critical to advanced PHP development is the use of namespaces. The arbitrarily defined namespace becomes a prefix to the class name, thereby avoiding the problem of accidental class duplication, and allowing you extraordinary freedom of development. Another benefit to the use of a namespace, assuming it matches the directory structure, is that it facilitates autoloading, as discussed in Chapter 1, Building a Foundation.

How to do it...

1. To define a class within a namespace, simply add the keyword namespace at the top of the code file:

   namespace Application\Entity;

   Note

   Best practice

   As with the recommendation to have only one class per file, likewise you should have only one namespace per file.

2. The only PHP code that should precede the keyword namespace would be a comment and/or the keyword declare:

   <?php
   declare(strict_types=1);
   namespace Application\Entity;
   /**
    * Address
    *
    */
   class Address
   {
     // some code
   }

3. In PHP 5, if you needed to access a class in an...