Extend Wordpress functionality with shortcodes

Two useful shortcodes, that you can add to your functions.php file (if you’re not using the Mystique theme):

Allowing the user to insert a arbitrary widget inside posts:

<?php
function widget($atts){
global $wp_widget_factory;
extract(shortcode_atts(array(
'class' => FALSE // the widget's PHP class name, required
), $atts));
// make sure the user doesn't XSS us (wpmu)
$class = wp_specialchars($class);
//check if the class exists
if (!is_a($wp_widget_factory->widgets[$class], 'WP_Widget')):
// if it doesn't, then try to add WP_Widget_ in front of the class name, and check again
$wp_class = 'WP_Widget_'.ucwords($class); // capitalize 1st letter
if (!is_a($wp_widget_factory->widgets[$wp_class], 'WP_Widget')):
$wp_class = 'WP_Widget_'.ucwords(strtolower($class));
if (!is_a($wp_widget_factory->widgets[$wp_class], 'WP_Widget')):
return '<p>'.sprintf(__("%s: Widget class not found. Make sure this widget exists and the class name is correct"),'<strong>'.$class.'</strong>').'</p>';
else:
$class = $wp_class;
endif;
endif;
// checking for other attributes, other than "class"
$instance = array();
foreach($atts as $att=>$val):
if ($att!="class") $instance[wp_specialchars($att)]=wp_specialchars($val);
endforeach;
$id = $class; // name the selector id as the PHP class name
// this is the css class, not the PHP class name
$classname = $wp_widget_factory->widgets[$class]->widget_options['classname'];
// if doesn't exist, name it as the id (class name)
if(!$classname) $classname = $id;
// change the id to the widget id parameter, if set
if(isset($instance['widget_id'])) $id= $instance['widget_id'];
// output to php buffer, because there's not get_the_widget function in wp
ob_start();
// display the widget
the_widget($class, $instance, array('widget_id'=>'arbitrary-instance-'.$id,'before_widget' => '
','after_widget' => '
','before_title' => '
','after_title' => '
'));
// store the buffer output in a variable
$output = ob_get_contents();
ob_end_clean();
// display it
return $output;
}
add_shortcode('widget','widget'); // registers the shortcode

To use this add in your posts for example:
[widget  class="calendar"]
A more detailed explanation here.

Display certain posts  inside pages:

<?php
function queryposts($atts){
extract( shortcode_atts( array(
'category_id' => '',
'category_name' => '',
'tag' => '',
'day' => '',
'month' => '',
'year' => '',
'count' => '5',
'author_id' => '',
'author_name' => '',
'order_by' => 'date',
), $atts));
$output = '';
$query = array();
// create the query string
if ($category_id != '') $query[] = 'cat=' .$category_id;
if ($category_name != '') $query[] = 'category_name=' .$category_name;
if ($tag != '') $query[] = 'tag=' . $tag;
if ($day != '') $query[] = 'day=' . $day;
if ($month != '') $query[] = 'monthnum=' . $month;
if ($year != '') $query[] = 'year=' . $year;
if ($count) $query[] = 'posts_per_page=' .$count;
if ($author_id != '') $query[] = 'author=' . $author_id;
if ($author_name != '') $query[] = 'author_name=' . $author_name;
if ($order_by) $query[] = 'orderby=' . $order_by;
ob_start(); // output to buffer
// backup the $post variable so it doesn't mess it up if called again
$backup = $post;
$posts = new WP_Query(implode('&',$query));
while ($posts->have_posts()): $posts->the_post();
// copy here the post layout from your theme's index.php file -- this is just a example ?>
endwhile;
$post = $backup; // restore the original $post
wp_reset_query();
// store the buffer output in the $output variable
$output = ob_get_contents();
ob_end_clean();
return $output;
}
add_shortcode('query', 'queryposts'); // add the shortcode...

Example:
[query category_name="Uncategorized" count=15]