Check if a shortcode exists in WordPress

shortcode-exists.php

<?php

if ( ! function_exists( 'shortcode_exists' ) ) :
/**
 * Check if a shortcode is registered in WordPress.
 *
 * Examples: shortcode_exists( 'caption' ) - will return true.
 *           shortcode_exists( 'blah' )    - will return false.
 * 
 * @param string $shortcode The name of the shortcode to check
 * @return bool Whether the shortcode exists or not
 */
function shortcode_exists( $shortcode ) {
	global $shortcode_tags;
	return array_key_exists( $shortcode, $shortcode_tags ) );
}
endif;