Dynamic access and usage skills of PHP namespace (namespace), namespace namespace_PHP tutorial

Dynamic access and usage skills of PHP namespace (namespace), namespace namespace

PHP’s namespace (namespace) is the most important new feature added in PHP 5.3. This concept has been in C# for a long time. Namespace in PHP is actually the same concept as C#.

1. Dynamic access to namespace elements

namespace me\poet;
function test()
{
  echo '1111';
}
$fun = 'test';//不能这么用，最后$fun()无法动态调用到test():Fatal error: Call to undefined function test()
$fun = '\me\poet\test';//正确
//$fun = 'me\poet\test';//正确
$fun();

In other words, the dynamic call must be a qualified name or a fully qualified name (Conceptual reference: Basics of using PHP namespaces)

2. Magic constants and operators

namespace me\poet;
function test()
{
  echo '1';
}
echo __NAMESPACE__;　//魔术常量:命名空间的名称（输出 me\poet）
//namespace操作符：显式访问当前命名空间或子命名空间中的元素，等价于类中的self操作符
\me\poet\test();
namespace\test();
//上两行代码等价。

3. Alias, import and global space (including multiple examples)

namespace ws\weichen\www;
use ws\weichen\www as poet;//定义别名poet
//use ws\weichen\www; //不加as，则取最后的作为别名（www）
function demo()
{
  echo '1';
}
\ws\weichen\www\demo();
poet\demo();
//www\demo();　　　　//不加as的情况，则这样调用

The above three lines of code have the same effect.
The advantage of naming according to the rules (wsweichenwww): If you change the domain name, you only need to change the prefix name, which will not affect the use of the alias www in the subsequent code.

/* 导入 */
include 'hello.class.php';
use \ws\weichen\www;
use \Hello;
/*--------------------------------------------------------*/
/* 支持多个use语句 */
use \nihao\shijie as hello, \ws\weichen\www;
/*--------------------------------------------------------*/
/* 全局空间:反斜线调用 */
namespace A\B\C;
//这个函数是 A\B\C\fopen();
function fopen()
{
  $f = \fopen('demo.txt');//调用全局fopen函数
  return $f;
}

php namespace Namespace error?

No problem with grammar.

What is your PHP version? PHP supports namespaces starting from version 5.3.0. Your PHP version may be lower.

php use php namespace What is going on

1. namespace Zend\Http\PhpEnvironment;

This code defines a namespace, which you can understand as defining a domain name named Zend\Http\PhpEnvironment.

After definition, the classes, interfaces, const, etc. declared below are all in the declared "domain". When referencing an include file that declares a namespace, and if you want to call something in it, you must:

Adjust the current script to this domain name, otherwise, you have to use the full name of namesapce.

For example, inc.php file:

namespace Zend\Http\PhpEnvironment;
class Bar {}//define a class

when called by other files ：

// The first way to access Foo, use the full name
require 'inc.php';
$foo = new \Zend\Http\PhpEnvironment\Bar();

//The second method of accessing Foo
namespace Foo; //Adjust the current script to the ns domain of Foo, and the namespace declaration must be in the first sentence
require 'inc.php';
$foo = new Bar();

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

For example, the above

// is the first to access Foo This method uses the full name
require 'inc.php';
$foo = new \Zend\Http\PhpEnvironment\Bar();

After using uses, the writing is as follows:

use \Zend\Http\PhpEnvironment as pe; //Define alias

$foo = new \pe\Bar(); //Use short alias to replace original

if Omit the following as...., then you can directly replace it with the text of the last section, for example, the above:

use \Zend\Http\PhpEnvironment; //Define alias
$ foo = new \PhpEnvironment\Bar(); //Replace the original

======================== with a short alias ========================

Relevant content in the official PHP manual:

In PHP, namespace naming Space is used to solve two types of problems encountered when creating reusable code such as classes or functions when writing class libraries or applications:

1. User-written code and PHP internal classes/functions/constants Or name conflicts between third-party classes/functions/constants.
2. Create an alias (or short) name for a very long identifier name (usually defined to alleviate the first type of problem) to improve the readability of the source code.

PHP namespaces provide a way to group related classes, functions, and constants together.

PHP namespace supports two ways of using aliases or imports: using aliases for class names, or using aliases for namespace names. Aliases are implemented through the operator use. ...The rest of the text>>

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