A shortcode are a great customizable feature of WordPress that is basically a placeholder for other content.

When implemented on the Dashboard side in the WYSIWYG editor, it will look like:

[newsletter title="this is a different title"]

And perhaps appear something like:

My example here is a shortcode where a newsletter signup can be placed within a post or page’s content. It has a default attribute set for the title but if the user wants it to have a different title, they can add different content. For brevity’s sake in this case, newsletter() hypothetically drop in the markup for the signup fields.

Shortcode Snippet

function newsletter_shortcode( $passed_values ) {

	$attributes = shortcode_atts( array(
		'title' => 'I\'d love to write to you',
	), $passed_values );

	return "<div class='newsletter'><h3>" . $attributes['title'] . '</h3>' . newsletter() . '</div>';
}
add_shortcode( 'newsletter', 'newsletter_shortcode' );

Parameters:

The add_shortcode function requires two parameters, both of which are under our control.

1. 'newsletter': What you want to name your shortcode and utilize between square brackets in the WordPress WYSIWYG where you want the markup to appear.
2. ''newsletter_shortcode'':The name of the function which handles the output.

Shortcode Usage:

If you wanted to utilize the shortcode but not pass in a different title, you would use the more pared down version without passing the attribute (because we have a ‘backup’ set):

[newsletter]

Which would perhaps appear something like:

Additional Reading:

• WordPress Codex: Shortcode API
• WordPress Codex: add_shortcode