What is the right way to include plugins files in plugin system - php

Question

I've created a plugins system, and I've created everything in that system except, how can I inclusion plugins files to execute it.
I'm tried to create a method, Which is doing include plugins files to execute it.
-- Firstly -- :
The method that get all plugins files, and that begin with index word which indicates the main file of plugin (i.g. index-pluginName.php), and add the path and file name to an array.
public function getPluginFiles($plugin_folder) {
$dir = opendir($plugin_folder);
while ($files = readdir($dir)) {
if ($files == '.' || $files == '..')
continue;
if (is_dir($plugin_folder.'/'.$files))
$this->getPluginFiles($plugin_folder.'/'.$files);
if (preg_match('/^[index]+/i', $files)) {
$this->plugins_path[$plugin_folder.'/'.$files] = $files;
}
}
closedir($dir);
}
-- secondly -- :
The method that include all the main file of plugins to execute, and this method get the path and name of plugin file from the array that created earlier .
public function includePlugFiles() {
$this->getPluginFiles($this->plugin_folder);
foreach ($this->plugins_path as $dir=>$file) {
include_once (dirname($dir)."/".$file);
}
}
Also see an example of code that exists in plugin file:
function test() {
echo " This is first plugin <br/>";
}
$plugin->addHook('top', test); // parameters(top=position, test=callback)
Now, when I create an instance of the object to be this form .
$plugin = new plugin;
$plugin->includePlugFiles();
But after all this, shows error message
Fatal error: Call to a member function addHook() on a non-object in .... projects\plugins\index-test.php on line 7
This is the code of line 7:
$plugin->addHook('top', test); // parameters(top=position, test=callback)
I know the problem occur because, the object will not be created.
and the problem is can't create the object in every main plugin file.

Answer 1

It's probably not the cleanest solution, but instead of trying to reference the $plugin symbol (which is outside the scope of the plugin file), you could also do this:
$this->addHook('top', test);
Alternatively, you could explicitly create the reference inside the includePlugFiles() method:
public function includePlugFiles()
{
$plugin = $this;
$this->getPluginFiles($this->plugin_folder);
foreach ($this->plugins_path as $dir=>$file) {
include_once (dirname($dir)."/".$file);
}
}