Namespace_PHP Tutorial

Naming variables, functions and classes is quite difficult. In addition to considering that the name of the variable should be easy to understand, you also have to worry about whether the name has been used somewhere else. In a small script, the first The two questions are fundamental. When you consider reusing your code, the code in subsequent projects must avoid using the names you have used. Generally speaking, reusable code is always contained in functions or classes, which requires a lot of processing Possible naming conflicts. But naming conflicts can also occur between functions and classes. You can try to avoid this by prefixing all classes, or you can use the namespace statement.

The Namespace keyword names a block of code. Outside this block of code, the script must use the operator:: plus the name of the namespace to reference this block of code. The same method is used to reference static class members. Code within the namespace does not You need to declare the namespace, which is the default. This method is better than adding a prefix. Your code will become more compact and readable.

You may be wondering whether it is possible to create hierarchical (nested) namespaces. The answer is no. But you can add a colon after the namespace name, and you can again call variables, functions, and Classes. Colons are allowed in namespaces as long as they are not the first and last characters or follow another colon. Colons in namespace names have no meaning to PHP, but if you use them to distinguish logical areas blocks, they are a great way to illustrate parent-child relationships in your code.


/* Note: You can use this:
namespace animal:dog {}
namespace animal:pig {}

Use colons to illustrate the parent-child relationship.
*/


You may not include anything other than function, class, or constant definitions within a namespace statement. This will prevent you from using them to improve older function libraries that use global variables. Namespaces are best suited for object orientation. Within a namespace Constants use the same syntax as constants in classes.

Example 6.17 shows how to use namespaces.

Listing 6.17 Using a namespace

namespace core_php:utility
{
class textEngine
{
public function uppercase($text) file://uppercase
{
return(strtoupper($text));
}
}

//make non-OO interface Create a non-OO interface
function uppercase($text)
{
$e = new textEngine;
return($e->uppercase($text));
}

}

//test class in namespace Test the class in the namespace
$e = new core_php:utility::textEngine;
print($e->uppercase("from object") . "
");

//test function in namespace Test function in namespace
print(core_php:utility::uppercase("from function") . "
");

//bring class into global namespace Bring class into global namespace
import class textEngine from core_php:utility;
$e2 = new textEngine;
?>
The Import statement imports a certain part of the namespace into the global namespace.
To import members of a single namespace, you can specify the type as constant, function or class, and then write the name of the member;
//Such as import class XXX
If you want to import all members of a specific type, you can use * instead of the name;
//For example, import constant * imports all constants
If you want to import all members of all types, just use *.
//Such as import *

After the member, use the from keyword to add the name of the namespace.
//Such as import class textEngine from core_php:utility;

In short, you have to write a statement like import * from myNamespace or import class textEngine from core_php:utility, just like in Example 6.17.

http://www.bkjia.com/PHPjc/631947.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/631947.htmlTechArticleNaming variables, functions and classes is quite difficult. In addition to taking into account that the names of variables should be easy to understand, Worry about whether this name has already been used somewhere else. In a small script, section...