plugin.php

add_shortcode('five-o-clock', 'five_o_clock_here');
 
//Shortcode function that defines default values
function five_o_clock_here($atts) {
     $atts = shortcode_atts( array(
        'where' => 'somewhere!',
    ), $atts );
        
    return "It's 5 o' clock " . $atts["where"];