PHP / OOP - initializing class within a class
===

I am fairly new to OOP but not new to PHP. I am trying to initialize a class from within another class. 

index.php

    <?
    error_reporting(E_ALL);
    require("classes/memcache.php");
    require("classes/video_test.php");
    $videos = new video;
    ?>

video_test.php

    <?php
        class video {
    
                private $mcache;
    
                public function __construct() {
                $this->mcache = new MCACHE();
                }
    
                public static function get_scene($scene_id) {
                $info = $this->$mcache->get_item("mykey");
                }
    
    
        }
    ?>

Produces:
 PHP Fatal error:  Using $this when not in object context in 

