So i've been trying to auto load any external libraries ( like Mustache , PHPExcel ... ) , and all of them come's with an autoloader.php , but i tried to use the registerDirs , but i can't make it work , but if i load all of the classes manualy it works fine. Why so ?

(new \Mustache_Engine)->render("/contact.tpl", [ 
    'name' => $this->request->getPost("name") , 
    'message' => $this->request->getPost("message")
]);

This doesn't work:

$loader->registerDirs([
    '../libraries/Mustache/'
]);

This works:

$loader->registerClasses([
            'Mustache_Engine'           => '../libraries/Mustache/Engine.php',
            'Mustache_Cache'            => '../libraries/Mustache/Cache.php',
            'Mustache_Compiler'         => '../libraries/Mustache/Compiler.php',
            'Mustache_Context'          => '../libraries/Mustache/Context.php',
            'Mustache_Exception'        => '../libraries/Mustache/Exception.php',
            'Mustache_HelperCollection' => '../libraries/Mustache/HelperCollection.php',
            'Mustache_LambadaHelper'    => '../libraries/Mustache/LambadaHelper.php',
            'Mustache_Loader'           => '../libraries/Mustache/Loader.php',
            'Mustache_Logger'           => '../libraries/Mustache/Logger.php',
            'Mustache_Parser'           => '../libraries/Mustache/Parser.php',
            'Mustache_Template'         => '../libraries/Mustache/Template.php',
            'Mustache_Tokenizer'        => '../libraries/Mustache/Tokenizer.php',

            'Mustache_Cache_AbstractCache'     => '../libraries/Mustache/Cache/AbstractCache.php',
            'Mustache_Cache_FilesystemCache'   => '../libraries/Mustache/Cache/FilesystemCache.php',
            'Mustache_Cache_NoopCache'         => '../libraries/Mustache/Cache/NoopCache.php',

            'Mustache_Loader_StringLoader'     => '../libraries/Mustache/Loader/StringLoader.php',
            'Mustache_Loader_MutableLoader'    => '../libraries/Mustache/Loader/MutableLoader.php',
            'Mustache_Loader_InlineLoader'     => '../libraries/Mustache/Loader/InlineLoader.php',
            'Mustache_Loader_FilesystemLoader' => '../libraries/Mustache/Loader/FilesystemLoader.php',
            'Mustache_Loader_CascadingLoader'  => '../libraries/Mustache/Loader/CascadingLoade.php',
            'Mustache_Loader_ArrayLoader'      => '../libraries/Mustache/Loader/ArrayLoader.php',

            'Mustache_Logger_AbstractLogger'   => '../libraries/Mustache/Logger/AbstractLogger.php',
            'Mustache_Logger_StreamLogger'     => '../libraries/Mustache/Logger/StreamLogger.php',

            'Mustache_Exception_InvalidArgumentException' => '../libraries/Mustache/Exception/InvalidArgumentException.php',
            'Mustache_Exception_LogicException'           => '../libraries/Mustache/Exception/LogicException.php',
            'Mustache_Exception_RuntimeException'         => '../libraries/Mustache/Exception/RuntimeException.php',
            'Mustache_Exception_SyntaxException'          => '../libraries/Mustache/Exception/SyntaxException.php',
            'Mustache_Exception_UnknownFilterException'   => '../libraries/Mustache/Exception/UnknownFilterException.php',
            'Mustache_Exception_UnknownHelperException'   => '../libraries/Mustache/Exception/UnknownHelperException.php',
            'Mustache_Exception_UnknownTemplateException' => '../libraries/Mustache/Exception/UnknownTemplateException.php',
        ]);