I would like to know the "best" – OOP-way – and WP-compatible – format for instantiating an object, while passing arguments ( which are defined as properties in the parent class ) – which are then cleanly and correctly available to all sub classes, which extend the parent.

I would like to know how to make $this->slug ( the parent prop ) available cleanly within the sub class, without having to pass the arguments to this class constructor.

The example code below works, but something smells wrong:

<?php

// plugin.php

namespace QPlugin;

// Define Class ##
class Plugin {

    // class properties ##
    protected $slug     = false;

    // construct ##
    public function __construct( Array $args = [] ) {

        // set class props, if defined - check using null coalescing operator ##
        $this->slug     = $args['slug'] ?? false ;

    }

    // public init callback ##
    public function init() {

        // setup CPT ##
        $cpt = new QPluginCPT([
            'slug'      => $this->slug,
        ]);
        $cpt->init();

    }

}

// instantiate the plugin class and make the returned object available as a (optional) global variable  ##
global $q_plugin;
$q_plugin = new Plugin([
    'slug'      => 'q_cpt', // cpt slug -- singular ##
]);
$q_plugin->init();

// NAMESPACE/cpt.php

namespace QPluginCPT;

class CPT {

    // construct ##
    public function __construct( Array $args = [] ) {

        // store passed args ##
        $this->args = $args;

    }

    // public init callback ##
    public function init() {

        // sanity ##
        if( 
            ! isset( $this->args['slug'] ) 
        ){

            error_log( 'Error in params passed to '.__CLASS__ );

            return false;

        }

        // $this->args['slug'] is now available to use in register_post_type function
        // BUT, I would like to know how to make $this->slug ( the parent prop ) available cleanly, without having to pass the arguments to this class constructor

    }

}

Thanks!