Ticket #7092: hakre-commentsfeedlength-7092.php

<?php
/**
 * @author  hakre <http://codex.wordpress.org/User:Hakre>
 * @see     http://core.trac.wordpress.org/ticket/7092
 * @license GPL v3
 * @version 0.1.2
 * 
 * @-wp-plugin Plugin Name: commentsfeedlength
 * @-wp-plugin Plugin URI: http://core.trac.wordpress.org/ticket/7092
 * @-wp-plugin Description: separate setting for limiting comments feed
 * @-wp-plugin Author: hakre
 * @-wp-plugin Version: 0.1
 * @-wp-plugin Author URI: http://codex.wordpress.org/User:Hakre
 */

commentsfeedlengthPlugin::bootstrap();

/**
 * commentsfeed length plugin class
 */
class commentsfeedlengthPlugin {        
        /**
         * instance local store
         * @var rssfeedlengthPlugin
         */
        static $_instance = null;

        protected $_option = 'comments_per_rss';
        
        /**
         * option getter - local helper
         * 
         * @return int option value
         */
        private function _get_option() {                
                $value = abs(intval(get_option($this->_option)));
                return (int) $value;
        }

        /**
         * plugin bootstrap to reduce interference with the global symbol table 
         * @return void
         */
        public static function bootstrap() {
                if( null == commentsfeedlengthPlugin::$_instance ) {
                        commentsfeedlengthPlugin::$_instance = new commentsfeedlengthPlugin();
                } 
        }

        /**
         * plugin constructor
         */
        public function __construct() {
                add_action('admin_init', array($this, 'admin_init'));
                add_filter('comment_feed_limits', array($this, 'comment_feed_limits'));         
        }

        /**
         * admin_init
         * 
         * @-wp-action admin_init
         * @return void
         */
        public function admin_init() {

                if (false === get_option($this->_option)) {                     
                        update_option($this->_option, get_option('posts_per_rss'));     
                }
                
                $key   = $this->_option;
                $title = __('Syndication feeds show the most recent');
                $callb = array($this, 'settings_field_input_callback');
                $args  = array(
                                'label_for' => $key,
                                'for_text' => __('comments')
                );

                add_settings_field($key, $title, $callb, 'reading', 'default', $args);
                register_setting('reading', $key);
        }

        /**
         * comment_feed_limits
         * 
         * @-wp-action comment_feed_limits
         * @param  string $limit LIMIT clause for SQL query
         * @return string filtered $limit parameter
         */
        public function comment_feed_limits($limit) {           
                return sprintf('LIMIT %d', $this->_get_option());
        }

        /**
         * field input callback 
         * 
         * used by self::admin_init()
         * 
         * @param  array $args
         * @return void
         */
        public function settings_field_input_callback($args) {          
                extract($args);         
                printf(
                        '<input name="%1$s" type="text" id="%1$s" value="%2$d" class="small-text" /> %3$s'
                        , $label_for, $this->_get_option(), $for_text
                );
        }

} // class commentsfeedlengthPlugin