PHP Namespaces
Namespaces are qualifiers that solve two different problems:
- Name collisions between code you create, and internal PHP classes/functions/constants or third-party classes/functions/constants.
- Ability to alias (or shorten) Extra_Long_Names that are designed to alleviate the first problem.
Think of namespaces like directories in a file system. You can have foo.txt in directory A and foo.txt in directory B, and they won't conflict.
1. Defining a Namespace
Namespaces are declared at the very top of a file using the namespace keyword.
<?php
namespace Html;
class Table {
public $title = "";
public $numRows = 0;
}
?>2. Using Namespaces
If you are inside a namespace, you can access other classes in the same namespace directly. To access classes from outside, you must use the full path (starting with a backslash \).
$table = new \Html\Table();3. The use Keyword
You can import classes from other namespaces to avoid typing the full path every time.
<?php
namespace Page;
use Html\Table;
$table = new Table();
?>