PHP - most lightweight psr-0 compliant autoloader

Question

I have a tiny application that i need an autoloader for. I could easily use the symfony2 class loader but it seems like overkill.

Is there a stable extremely lightw

Answer 1

The PSR-0 specification document has an examplary compatible autoloader function that is already pretty short:

function autoload($className)
{
    $className = ltrim($className, '\\');
    $fileName  = '';
    $namespace = '';
    if ($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';

    require $fileName;
}

It's usage is pretty straight forward:

spl_autoload_register('autoload');

The shortcoming with it is, that you need to configure base-directories it works on with the include_path directive. To support a hybrid PSR-0 autoloaders leaned onto SPL semantics, the following one supportss include path and spl autoload extensions:

$spl_autoload_register_psr0 = function ($extensions = null) 
{
    $callback = function ($className, $extensions = null) 
    {
        if (!preg_match('~^[a-z0-9\\_]{2,}$~i', $className)) {
            return;
        }
        null !== $extensions || $extensions = spl_autoload_extensions();
        $extensions = array_map('trim', explode(',', $extensions));
        $dirs = array_map('realpath', explode(PATH_SEPARATOR, get_include_path()));

        $classStub = strtr($className, array('_' => '/', '\\' => '/'));

        foreach ($dirs as $dir) {
            foreach ($extensions as $extension) {
                $file = sprintf('%s/%s%s', $dir, $classStub, $extension);
                if (!is_readable($file)) {
                    continue;
                }
                include $file;
                return;
            }
        }
    };

    return spl_autoload_register($callback);
};

The The Symfony2 ClassLoader Component has the benefit to allow more configuration here. You can install it easily via Pear or Composer (symfony/class-loader on Packagist). It is a component on it's own that is used by many and fairly well tested and supported.