To people coming here by searching about namespaces, know that a consortium has studied about best practices in PHP, in order to allow developers to have common coding standards.
These best practices are called "PHP Standard Recommendations" , also known as PSR.
They are visible on this link : http://www.php-fig.org/psr
Actually there are 5 coding standards categories :
PSR-0 : Autoloading Standard , which goal is to make the use of Namespaces easier, in order to convert a namespace into a file path.
PSR-1 : Basic Coding Standard , basically, standards :)
PSR-2 : Coding Style Guide, where to put braces, how to write a class, etc.
PSR-3 : Logger Interface , how to write a standard logger
PSR-4 : Improved Autoloading , to resolve more Namespaces into paths.
The ones I want to point are PSR-0 and PSR-4 : they use namespaces to resolve a FQCN (Fully qualified class name = full namespace + class name) into a file path.
Basic example, you have this directory structure :
./src/Pierstoval/Tools/MyTool.php
The namespacing PSR-0 or PSR-4 standard tells that you can transform this path into a FQCN.
Read the principles of autoload if you need to know what it means, because it's almost mandatory ;) .
Structure :
{path}/autoloader.php
{path}/index.php
{path}/src/Pierstoval/Tools/MyTool.php
Files :
<?php
// {path}/index.php
include 'autoloader.php';
$tool = new Pierstoval/Tools/MyTool();
?>
<?php
// {path}/src/Pierstoval/Tools/MyTool.php
namespace Pierstoval\Tools;
class MyTool {}
?>
<?php
// {path}/autoloader.php
function loadClass($className) {
$fileName = '';
$namespace = '';
// Sets the include path as the "src" directory
$includePath = dirname(__FILE__).DIRECTORY_SEPARATOR.'src';
if (false !== ($lastNsPos = strripos($className, '\\'))) {
$namespace = substr($className, 0, $lastNsPos);
$className = substr($className, $lastNsPos + 1);
$fileName = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
}
$fileName .= str_replace('_', DIRECTORY_SEPARATOR, $className) . '.php';
$fullFileName = $includePath . DIRECTORY_SEPARATOR . $fileName;
if (file_exists($fullFileName)) {
require $fullFileName;
} else {
echo 'Class "'.$className.'" does not exist.';
}
}
spl_autoload_register('loadClass'); // Registers the autoloader
?>
A standardized autoloader will get the class you want to instanciate (MyTool) and get the FQCN, transform it into a file path, and check if the file exists. If it does, it will <?php include(); ?> it, and if you wrote your class correctly, the class will be available within its correct namespace.
Then, if you have the following code :
<?php $tool = new Pierstoval/Tools/MyTool(); ?>
The autoloader will transform the FQCN into this path :
{path}/src/Pierstoval/Tools/MyTool.php
This might be the best practices ever in PHP framework developments, such as Symfony or others.