About PHP namespace (combined with code examples, simple and easy to understand)

The following is the namespace of PHP that I have compiled for you. Interested students can take a look.

The first file
cat.class.php

<?php
namespace Animals\Cat;        
class Cat    
{        
    public function speak()        
    {            
        echo &#39;miaow&#39;;        
    }    
}    
    function root()
    {        
        return &#39;cat.class.php&#39;;
    }
?>123456789101112131415

The second file
dog.class.php

<?php
namespace Animals\Dog;    
    class Dog
    {
        public function speak()
        {
            echo &#39;woof&#39;;
        }
    }    class Cat
    {
        public function speak()
        {
            echo &#39;miaoth&#39;;
        }
    }    function root(){
        return &#39;dog.class.php&#39;;
    }
?>1234567891011121314151617181920212223

index.php
The third file is the file that loads the above namespace

<?php
    namespace Index;    
    require_once &#39;cat.class.php&#39;;    
    require_once &#39;dog.class.php&#39;;    
    use Animals\Cat;    
    use Animals\Dog as Snoopi;
        
    //完全限定名
    $cat1 = new \Animals\Cat\Cat();  
    $cat1->speak();    
    echo &#39;<br/>&#39;;    
    $cat2 = new \Animals\Dog\Cat();    
    $cat2->speak();    
    echo &#39;<br/>&#39;;    
    $dog1 = new \Animals\Dog\Dog();    
    $dog1->speak();    
    echo &#39;<br/>&#39;; 
       
    //非完全限定名
    $cat3 = new Cat\Cat();    
    $cat3->speak();    
    echo &#39;<br/>&#39;; 
       
    //别名 *别名和非完全限定名 不能同时使用
    $dog3 = new Snoopi\Dog();    
    $dog3->speak();    
    //不止函数，该命名空间下的任何可用资源都可调用[函数、变量、常量等等]
    echo Snoopi\root();    
    echo &#39;<br/>&#39;;
?>12345678910111213141516171819202122232425262728293031323334

The namespace class can be analogized to the file directory system
new A class in a namespace [or function, variable, etc. etc.] That is to call the content in a file in a certain directory
The fully qualified name is the path to find the content in the file
The non-fully qualified name is equivalent to
use the 'relative path' when introducing the namespace ' Assign a value to a variable, which defaults to the last subspace.
Use the as keyword to set the name of the variable. The variable is an alias, so aliases and non-fully qualified names cannot be used at the same time (because a use[ as] Only one alias can be given).
Analog file directory system:
File location: /root/path/file/fileContent;
use /root/path/file, that is, file='/root/path/file′, so the path of file is file='/root/path/file' so the path of file is file/fileContent
*And the namespace Index in index.php is equivalent to indicating the current file location
So if the namespace Index in index.php Modifying the file content to

<?php
    require_once &#39;cat.class.php&#39;;    
    require_once &#39;dog.class.php&#39;;    
    use Animals\Cat\Cat;#引入该命名空间下的类
    $cat4 = new Cat();    
    $cat4->speak();
    root(); 
?>123456789

use is equivalent to loading only the Cat class in the namespace Animals\Cat, and the root() function is not 'loaded'
So the operation will throw an error: root( )Function not declared

The above is the PHP namespace I compiled for everyone. I hope it will be helpful to everyone in the future.

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