PHP namespace behaviour gives FATAL error with spl_autoload_register - namespaces

Question

I want to use namespace and spl_autoload_register together but failed with different error each time.
Please See complete code files on github.
Below are the files
a base file where create a class with namespace class.alpha.php
an include file where I define spl_autoload_register include.php
an example file which instantiate the class object eg.php
Now when I create object from eg.php it gives FATAL error but when I comment namespace line in class.alpha.php then it's working
Please see the code below.
alpha.class.php
<?php
//namespace Alpha; //<< comment and uncomment this to regenerate the error
class Alpha
{
// public static $baseDir_;
public $dir = __DIR__;
public static $baseDir_;
public function __construct()
{
echo __FILE__."=>".__METHOD__;
var_dump(self::$baseDir_, $this->dir);
$firstDir = !empty(self::$baseDir_) ? self::$baseDir_ : $this->dir;
}
}
include.php
<?php //namespace Alpha\config;
spl_autoload_extensions(".php");
spl_autoload_register('loadclass');
function loadclass($class)
{
try {
if (is_readable(strtolower($class).".class.php")) {
include_once strtolower($class).".class.php";
}
} catch (Exception $e) {
print "Exception:". $e;
}
}
//#link http://php.net/manual/en/function.spl-autoload-register.php
// spl_autoload_register(__NAMESPACE__.'Alpha\Alpha()' );
eg.php
<?php
require_once 'include.php';
/** below code works by commenting 1st line on alpha.class.php
if we un comment then below code gives Fatal error: Class 'Alpha' not found */
Alpha::$baseDir_ = '/opt/lampp/archive/';
$obj_ = new Alpha();
var_dump(get_included_files());
var_dump($obj_);
/** now we define namespace Alpha on alpha.class.php */
// $ns_ = new Alpha\Alpha(); // Fatal error: Class 'Alpha\Alpha' not found
// var_dump($ns_);
/** not working even with use statement */
// use Alpha;
// use Alpha;
// $fn = new Alpha\Alpha();
// var_dump($fn);
Please help me out to solve this issue.
Thanks

Answer 1

Your autoloader is receiving a request for a class of "Alpha\Alpha" if you uncomment the namespace in alpha.class.php and place the use Alpha\Alpha in eg. This means that the location it's expecting to find your class in would be alpha\alpha.class.php.
Unless you're on Windows, directory separators are typically forward slash (/). So there's a number of possible solutions.
**Possible Solution #1 - Leave all files in the same place **
If you want to leave everything where it is now, you'll need to remove the namespace from the class names in the autoloader. If you add these lines to the top of your autoloader, that will make it behave that way:
$classParts = explode("\\", $class);
$class = $classParts[count($classParts) - 1];
I would not recommend this solution though since it means that you can no longer provide the same class name in a different namespace.
Possible Solution #2 - Put namespaces in subdirectories
For this solution, you'd create a new directory "alpha" and move "alpha.class.php" into it. For autoloader changes, you can add the following lines to the top of your autoloader:
$class = str_replace("\\", "/", $class);
This will change the namespace separators from backslashes to file path separators with forward slash. This will work on windows as well as mac and linux.
Possible Solution #3 - Follow an established autoloading standard
There are already a number of standard PHP autoloading standards. PSR-0 (now deprecated) works, but PSR-4 would be recommended:
PSR-0: http://www.php-fig.org/psr/psr-0/
PSR-4: http://www.php-fig.org/psr/psr-4/
One big upside of following one of these standards is that there are already plenty of implementations for them and there's been a lot of thought put into how they should work and maintain compatibility with other libraries you may end up wanting to use. Composer (http://getcomposer.org) will allow you to set up and use both PSR-0 and PSR-4 style autoloaders based on a very simple configuration.
Anyway, for the TL;DR crowd, the issue is that the autoloader receives the entire namespaced path in order to know how to load the class. The fatal error was because the autoloader wasn't properly mapping from that namespaced class to a file system location, so the file containing the class was never being loaded.
Hope this helps.