WordPress Object-oriented plugin skeleton - http://snippets.khromov.se/a-nicer-way-to-structure-your-plugin/

your_plugin.php

<?php
/*
Plugin Name: Your Plugin
Plugin URI: http://snippets.khromov.se/a-nicer-way-to-structure-your-plugin/
Description: Your plugin skeleton
Version: 1.0
Author: you
Author URI: http://your-site.com
License: GPL2
*/
 
/* The class encapsulates the plugin and its functions */
class Your_Plugin
{
    /* Put any plugin variables here */
    var $plugin_variable;
 
    /* The constructor will be used to setup actions and filters */
    function __construct()
    {
        /**
         * Set a plugin variable
         */
        $this->plugin_variable = 'test';
 
        /**
         * Hook on plugins_loaded. This is the first hook available to regular plugins.
         * It happens when all plugins have been initialized and is the best place to put your logic.
         */
        add_action('plugins_loaded', array($this, 'plugin_loaded'));
 
        /* Optionally, add additional hooks here. */
    }
 
    /**
     * Put your main plugin logic here!
     */
    function plugin_loaded()
    {
        /* Here is how to call a function inside your class: */
        $sum = $this->add(1,2);
    }
 
    /**
     * A plugin function that adds
     * two numbers together and
     * returns them.
     *
     * @param $var1
     * @param $var2
     * @return mixed
     */
    function add($var1, $var2)
    {
        return $var1+$var2;
    }
}
 
/* This initiates your plugin */
$your_plugin = new Your_Plugin();