Example usage of custom fields and shortcode parameters in WordPress CMS

WordPress CMS has a lot of useful features e.g. shortcodes, custom fields.
Look at the code example below:

function my_slider( $atts ) {
	global $post;

	extract( shortcode_atts( array(	'slide_category' => 0 ), $atts, 'slide_category' ) );
	/*
	...
	*/	
	$args = array(
		'post_type'  => 'slide',
		'showposts'  => -1,
		'meta_query' => array(
			array(
				'key'   => 'slide_category',
				'value' => $slide_category,
			)
		)
	);
	$qry = new WP_Query($args);
	/*
	...
	*/

}

/*
...
*/
add_shortcode('mySlider', 'my_slider');

In example above it allows to output slides of exact category on page.
Possible slider shortcode usage can be:

[mySlider slide_category="1"]

Where mySlider is shortcode, slide_category is shortocode attribute which allows us to display flides of particular category.
To set slide_category – custom field should be added to each slide with slide category id.