Specific usage methods of namespace and use

namespace (hereinafter referred to as ns). After defining an ns, the class, interface, and const (excluding variables) declared below are all in the "domain" of the declared ns. When refers to a include file that declares ns, and if you want to call things in this ns, you must adjust the current script to this ns domain, otherwise you have to use the full name () to include it The full name of ns):

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// inc.php  
namespace Foo;  
class Bar {}  
// 访问Foo的第一种方法，用全称  
require 'inc.php';  
$foo = new \Foo\Bar();  
// 访问Foo的第二种方法  
namespace Foo; // 调整当前脚本到Foo这个ns域，而且namespace申明必须在第一句  
require 'inc.php';  
$foo = new Bar();

The purpose of the use keyword is to use the alias of ns:

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// 比如  
use A\Very\Long\Namespace as Ns;  
// 这样就可以用Ns来代替A/Very/Long/Namespace这个ns下定义的东西  
$foo = new Ns\Foo();

However, in some open source projects, we often see the usage of use Ns\Component without using as. This made me think about whether there is a second usage of use. The bad thing is that there is no description of this usage in the PHP documentation. I can only rely on guessing. Later, I thought about this problem carefully and came up with a more reliable one. The conclusion is that use can omit as and the following aliases and directly use the name of the last node of ns as an alias. Does it feel like the usage of the ln -s command:

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// 第三种用法  
require 'inc.php';  
use Foo\Bar; // 这样Bar就等于Foo\Bar了  
$foo = new Bar();

The above is what I compiled for everyone. The specific usage of namespace and use, I hope it will be helpful to everyone in the future.

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