When shortcodes are used with parameters, these extra pieces of data are sent to the associated processing function in the $atts parameter variable. By using a combination of the standard PHP extract and WordPress-specific shortcode_atts functions, our plugin is able to parse the data sent to the shortcode and create an array of identifiers and values that are subsequently transformed into PHP variables that we can use in the rest of our shortcode implementation function. In this specific example, we expect a single variable to be used, called user_name, which will be stored in a PHP variable called $user_name. If the user enters the shortcode without any parameter, a default value of ylefebvre will be assigned to the username variable to ensure that the plugin still works. Since we are going to accept user input in this code, we also verify that the user did not provide an empty string and we use the esc_html and esc_url functions to remove any potentially harmful HTML characters from the input string and make sure that the link destination URL is valid.

Once we have access to the Twitter username, we can put together the required HTML code that will embed a Twitter feed in our page and display the selected user's tweets.

While this example only has one argument, it is possible to define multiple parameters for a shortcode.