WP Shortcode example

test.php

<?php
//add the shortcode
add_shortcode(
    'testgetusers',         //name of the shortcode [getusers]
    'sample1'    //the function associated with the shortcode ( get_site_users() )
);

function sample1($attributes,$content){

    //make sure there is a value for each attribute
    //If a value is not set, make it the default
    $shortcode_values = shortcode_atts(
        array('color' => '#666'),
        $attributes
    );

    //if the content is set (not empty) wrap it in H3 tags
    if(isset($content)){
        echo '<h3>'.$content.'</h3>';
    }

    //get an array of all the users
    $users = get_users();

    echo '<ol style="color:' . $shortcode_values['color'] . '">';

    //get the Display Name of each user, wrap it in <li>
    foreach($users as $single_user){
        echo '<li>' . $single_user->display_name . '</li>';
    }

    echo '</ol>'; //close the Ordered List
}