Base WordPress shortcode example. This is a little shortcode boilerplate function.

wordpress_shortcode_example.php

<?php
/** 
* WordPress Shortcode Example
* Usage: [shortcode_example option="..."]
*/

// Shortcode Handle Function
function shortcode_example_function( $atts ) {
	$a = shortcode_atts( array(
 		'option' => "This is the default option value" // default options array
	), $atts );
	
	// 
 	if( !empty($a['option']) ) return "This is the shortcode output " . $a['option'];
}

// Add the shortcode
add_shortcode( 'shortcode_example', 'shortcode_example_function' );