<?php

/*

Plugin Name: Related Posts by Category

Plugin URI: http://playground.ebiene.de/400/related-posts-by-category-the-wordpress-plugin-for-similar-posts/

Description: The WordPress Plugin for similar posts grouped by category. It's small. It's fast. Really.

Author: Sergej Müller

Version: 0.4

Author URI: http://www.wpseo.org

*/

function related_posts_by_category($params, $post_id = 0) {

$entries = array();

$output = '';

$limit = 0;

$type = '';

$order = '';

$orderby = '';

$post_id = intval($post_id);

if (!$post_id) {

$post_id = $GLOBALS['post']->ID;

}

if (isset($params['limit'])) {

$limit = intval($params['limit']);

}

if (isset($params['type']) && !empty($params['type'])) {

$type = ($params['type'] == 'page' ? 'page' : 'post');

}

if (isset($params['order']) && !empty($params['order'])) {

$order = (strtoupper($params['order']) == 'DESC' ? 'DESC' : 'ASC');

}

if (isset($params['orderby']) && !empty($params['orderby']) && preg_match('/^[a-zA-Z_]+$/', $params['orderby'])) {

$orderby = $params['orderby'];

}

$entries = $GLOBALS['wpdb']->get_results(

sprintf(

"SELECT DISTINCT object_id, post_title FROM {$GLOBALS['wpdb']->term_relationships} r, {$GLOBALS['wpdb']->term_taxonomy} t, {$GLOBALS['wpdb']->posts} p WHERE t.term_id IN (SELECT t.term_id FROM {$GLOBALS['wpdb']->term_relationships} r, {$GLOBALS['wpdb']->term_taxonomy} t WHERE r.term_taxonomy_id = t.term_taxonomy_id AND t.taxonomy = 'category' AND r.object_id = $post_id) AND r.term_taxonomy_id = t.term_taxonomy_id AND p.post_status = 'publish' AND p.ID = r.object_id AND object_id <> $post_id %s %s %s",

($type ? ("AND p.post_type = '" .$type. "'") : ''),

($orderby ? ('ORDER BY ' .(strtoupper($params['orderby']) == 'RAND' ? 'RAND()' : $orderby. ' ' .$order)) : ''),

($limit ? ('LIMIT ' .$limit) : '')

),

OBJECT

);

if ($entries) {

foreach ($entries as $entry) {

$output .= sprintf(

'%s<a href="%s" %s title="%s">%s%s%s</a>%s',

isset($params['before']) ? $params['before'] : '',

get_permalink($entry->object_id),

(isset($params['rel']) ? ('rel="' .$params['rel']. '"') : ''),

str_replace('"', '"', $entry->post_title),

isset($params['inside']) ? $params['inside'] : '',

$entry->post_title,

isset($params['outside']) ? $params['outside'] : '',

isset($params['after']) ? $params['after'] : ''

);

}

} else {

$output = $params['message'];

}

if (isset($params['echo']) === true && $params['echo']) {

echo $output;

} else {

return $output;

}

}

?>