Basis and Examples of PHP Namespace of namespace

The namespace of PHP (namespace) is the most important new feature added in PHP 5.3. This concept has been around for a long time in C #, and namespace in php is actually the same concept as c #.

1. The namespace of PHP mainly solves three kinds of conflicting problems: constants, functions and classes

Popular understanding: namespace is equivalent to building a directory, and the code below namespace is placed in the directory to distinguish it from the outside.

/*
|---------------------------------
|namespace Example 
|@ Black-eyed poet  <www.chenwei.ws>
|---------------------------------
*/
namespace myself;
function var_dump()
{
  echo 100;
}
var_dump();  　　　 　     // Call custom functions (relative path mode) 
\myself\var_dump();  　　　 // Call custom functions (absolute path mode)  
\var_dump(100);     // Call global (system function) 

Note: There can be no code before namespace, except declare (); Multiple files can use the same 1 namespace, but the contents defined under the 1 namespace cannot conflict. namespace supports child namespaces, such as namespace\ myself\ good, which is equivalent to the concept of multilevel directories.

2. Multiple namespaces in the same 1 file

1.

/**
 *  Same as 1 If multiple namespaces are used in the file, ,1 General writing 
 */
namespace nihao\shijie;
function demo()
{
 　　 //.......
}
namespace hello\world;
function test()
{
  //........
}

\nihao\shijie\demo();
\hello\world\test();

2.

/**
 *  Same as 1 If multiple namespaces are used in the file, it is recommended to enlarge curly braces 
 */
namespace nihao\shijie{
 　　 function test_one()
 　　 {
  //......
 　　 };
}
namespace hello\world{
 　　 function test_two()
 　　 {
  //........
 　　 }
}
\nihao\shijie\test_one();
\hello\world\test_two();

The same 1 file using multiple namespaces, mainly for the project will be a number of PHP scripts merged in the same 1 file, the actual use is not recommended!

3. Name resolution rules (several concepts)

1. Unqualified name: The name does not contain namespace delimiters, such as myself

2. Qualified name: The name contains a namespace delimiter, such as: nihao\ shijie

3. Fully qualified name: The name contains a delimiter and begins with a namespace delimiter, such as:\ nihao\ shijie (that is, the concept of absolute path)