ExpressionEngine: Extending a core or third party module or plugin

mod.extendedchannel.php

<?php
class ExtendedChannel {

    public __construct()
    {
        $this->EE = &get_instance();
    }
    
    public function extended_entries()
    {
        // Get params
        $some_param = $this->EE->TMPL->fetch_param('some_param');

        // Do something to get some custom data, in this case $entry_ids was an array of entry IDs
        // ...

        // Modify the template params
        $entry_ids = implode('|', $entry_ids);
        $this->EE->TMPL->tagparams['fixed_order'] = $entry_ids;

        // Include the class if it isn't included
        if(!class_exists('Channel'))
        {
            // First party modules or plugins
            require_once(APPPATH.'modules/channel/mod.channel.php');
    
            // Third party would be
            // require_once(PATH_THIRD.'package/mod.package.php');
        }

        // Create instance of Package class and call the tag you want to extend
        // It will use the parameters passed from the template, as well as
        // anything you have modified in tagparams
        $C = new Channel();
        $this->return_data = $C->entries();
        return $this->return_data;
    }
}

Yes, it would be a tiny bit more efficient to call the class directly the way I am doing. The main difference would be in the regex to find the generated {exp:channel:entries} tag and parse it's parameters.

I feel like calling the class directly is much more testable and easier to work with however, even if it is only a bit faster.

This is really helpful, thanks for posting! However, I notice that when modifying TMPL->tagparams array, EE seems to ignore search params. For example,

$this->EE->TMPL->tagparams['search:title'] = "foo";

Still returns entries without "foo" in the title. I know it's been a while since you posted this, but if in your experience you've ever come across this issue, I'd love to know how you got around it.