Dynamic Access and Using Skills 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. Dynamic access to the elements of the namespace

namespace me\poet;
function test()
{
  echo '1111';
}
$fun = 'test';// You can't use it like this. In the end, $fun() Cannot dynamically call to test():Fatal error: Call to undefined function test()
$fun = '\me\poet\test';// Correct 
//$fun = 'me\poet\test';// Correct 
$fun();

That is, the dynamic invocation must be a qualified name or a fully qualified name (concept reference: the basis for the use of the PHP namespace)

2. Magic constants and operators

namespace me\poet;
function test()
{
  echo '1';
}
echo __NAMESPACE__; 　 // Magic constant : The name of the namespace (output  me\poet ) 
//namespace Operator: Explicitly accesses the elements in the current namespace or child namespace, equivalent to the self Operator 
\me\poet\test();
namespace\test();
// The last two lines of code are equivalent. 

3. Aliases, imports, and global spaces (with multiple examples)

namespace ws\weichen\www;
use ws\weichen\www as poet;// Define aliases poet
//use ws\weichen\www; // Do not add as Take the last as the alias ( www ) 
function demo()
{
  echo '1';
}
\ws\weichen\www\demo();
poet\demo();
//www\demo(); 　　　　 // Do not add as Is called in the case of 

The above three lines of code have one effect.
Benefits of naming according to rules (ws\ weichen\ www): If the domain name is changed, the prefix name can be changed without affecting the use of alias www in the following code.

/*  Import  */
include 'hello.class.php';
use \ws\weichen\www;
use \Hello;
/*--------------------------------------------------------*/
/*  Support multiple use Statement  */
use \nihao\shijie as hello, \ws\weichen\www;
/*--------------------------------------------------------*/
/*  Global space : Backslash call  */
namespace A\B\C;
// This function is  A\B\C\fopen();
function fopen()
{
  $f = \fopen('demo.txt');// Call global fopen Function 
  return $f;
}