Namespaces overview
I agree with SR, the new namespaces feature has solved a number of problems for me which would have required horrible coding to solve otherwise.
An example use:
Say you are making a small script, and write a class to connect to a database, calling it 'connection'. If you find your script useful and gradually expand it into a large application, you may want to rename the class. Without namespaces, you have to change the name and every reference to it (say in inheriting objects), possibly creating a load of bugs. With namespaces you can drop the related classes into a namespace with one line of code, and less chance of errors.
This is by no means one of the biggest problems namespaces solve; I would suggest reading about their advantages before citicising them. They provide an elegant solutions to several problems involved in creating complex systems.
Defining namespaces
Although any valid PHP code can be contained within a namespace, only three type of code are affected by namespaces: classes, functions and constants.
Namespaces are declared using the namespace keyword. A file containing a namespace must declare the namespace at the top of the file before any other code.
Example #1 Declaring a single namespace
<?php
namespace MyProject;
const CONNECT_OK = 1;
class Connection { /* ... */ }
function connect() { /* ... */ }
?>
The only code construct allowed before a namespace declaration is the declare statement, for defining encoding of a source file. In addition, no non-PHP code may precede a namespace declaration, including extra whitespace:
Example #2 Declaring a single namespace
<html>
<?php
namespace MyProject; // fatal error - namespace must be the first statement in the script
?>
In addition, unlike any other PHP construct, the same namespace may be defined in multiple files, allowing splitting up of a namespace's contents across the filesystem.
add a note
User Contributed NotesDefining namespaces
David Drakard
07-Sep-2008 07:56
07-Sep-2008 07:56
Baptiste
14-May-2008 02:47
14-May-2008 02:47
There is nothing wrong with PHP namespaces, except that those 2 instructions give a false impression of package management.
... while they just correspond to the "with()" instruction of Javascript.
By contrast, a package is a namespace for its members, but it offers more (like deployment facilities), and a compiler knows exactly what classes are in a package, and where to find them.
Anonymous
01-Apr-2008 02:11
01-Apr-2008 02:11
@ RS: Also, you can specify how your __autoload() function looks for the files. That way another users namespace classes cannot overwrite yours unless they replace your file specifically.