php名称空间：需要限定哪些条件？

Question

I am new to using namespaces in PHP and they seem very simple. However, when I added a namespace to the top of a large file containing classes, interfaces, and closures, the code stopped working altogether. Apparently some elements are not qualified properly.

For example:

<?php
namespace MyNamespace;
interface MyInterface { ... }
class MyClass implements MyInterface { ... }
...

I read the documentation at php.net, but I couldn't find a simple list of elements that require qualification under a single named space (either globally or otherwise).

So my question is, if you simply declare a namespace at the top of an otherwise namespace-free file, what elements would require qualification in that scenario?

Answer 1

The way you have it now with everything in one file like that, every class, interface or function in that file is now in the MyNamespace namespace. So from within those classes, interfaces and functions, if you want to refer to a class that is in a different namespace (global or named) you must use it's fully qualified name (or use use statements to declare aliases at top of the file). Note: pre-pending a \\ will get you to the global namespace.

Additionally, from outside of the file, if you want to access one of those classes, interfaces or functions you must use the fully qualified name.

MyNamespace\MyInterface
MyNamespace\MyClass

I should also mention, this is not a typical set up. According to psr standards, you should have only 1 class per file. Take a look at http://www.php-fig.org/ for more guidance on standards and practices.