Question

I want to create a wordpress plugin that can catch POST/GET requests to a certain URL from outside, such that I can have external PHP code POSTing data to the wordpress plugin, which the plugin can then further handle internally.

I don’t want to create blog posts or pages from outside, I know the XML-RPC interface exists for that. I’m talking about posting data from outside into wordpress and then handling it further within a plugin.

I guess I could also directly connect to the WP DB but that is probably not a very clean solution and might break if I upgrade WP.

Answer 1

As you already know about WordPress XMRPC: Your plugin can register own functions for XMLRPC that listen to the request then. You can send a POST request to the XMLRPC endpoint then and the plugin function will be triggered then.

The following code-example is a simple plugin class that registers a function to the XMLRPC endpoint my.recieve. It shows how the callback function is registered to that string:

/**
 * XML RPC Plugin
 */
return RecievePostPlugin::bootstrap();

class RecievePostPlugin
{
    private static $instance;
    public static function bootstrap()
    {
        if (null === $this->instance)
             $this->instance = new __CLASS__;
        return $this->instance; 
    }
    public function __construct()
    {
        add_filter('xmlrpc_methods', array($this, 'addXMLRPCActions'));
    }
    public function addXMLRPCActions(array $methods)
    {
        $methods['my.recieve'] = array($this, 'recieveXMLRPCAction');
        return $methods;
    }
    public function recieveXMLRPCAction(array $arguments)
    {
       // your code here, POST can be accessed via $_POST
    }
}

If you dislike the XMLRPC overhead, you can just create a PHP file part of your plugin and request it. Then you need to take care yourself to load all WP functions you might want to use (e.g. database access etc.).