Shortcode to show instructor lists in WPMU coursepress pro

Shortcode to show instructor lists in WPMU coursepress pro.php

<?php
/*
* use [get_all_instructors]
* Change wp-content/plugins/ to correct plugins folder if you use a separate folder for plugins at line 9
*/

add_shortcode( 'get_all_instructors', 'get_all_instructors_cb' );
function get_all_instructors_cb() {
	include ABSPATH . 'wp-content/plugins/coursepress/includes/classes/class.instructorsearch.php';
	if ( isset( $_GET['page_num'] ) ) {
		$page_num = ( int ) $_GET['page_num'];
	    } else {
		$page_num = 1;
	    }
	    
	    if ( isset( $_GET['s'] ) ) {
		$usersearch = $_GET['s'];
	    } else {
		$usersearch = '';
	    }
	$wp_user_search = new Instructor_Search( $usersearch, $page_num );
	$html = '<table class="instructor_list" width="100%">';
	$html .= '<tr>';
		$html .= '<th>Username</th>';
		$html .= '<th>First Name</th>';
		$html .= '<th>Surname</th>';
		$html .= '<th>Registered</th>';
		$html .= '<th>Courses</th>';
	$html .= '</tr>';
	foreach ( $wp_user_search->results as $user ) {
		$user_object = new Instructor( $user->data->ID );
		$html .= '<tr>';
			$html .= '<td>'.$user_object->user_login.'</td>';
			$html .= '<td>'.$user_object->first_name.'</td>';
			$html .= '<td>'.$user_object->last_name.'</td>';
			$html .= '<td>'.$user_object->user_registered.'</td>';
			$html .= '<td>'.$user_object->courses_number.'</td>';
		$html .= '</tr>';
	}
	$html .= '</table>';
	$html .= '<style>.instructor_list td, .instructor_list th{width: 20% !important; text-align:center}</style>';
	return $html;
}