1. Navigate to the WordPress plugin directory of your development installation.
2. Navigate to the ch9-pop-up-dialog directory and then edit ch9-pop-up-dialog.php.

3. Find the ch9pud_load_scripts function and add the following highlighted lines of code:

function ch9pud_load_scripts() { 
    // Only load scripts if variable is set to true
    global $load_scripts;

    if ( $load_scripts ) {
        wp_enqueue_script( 'jquery' );
        add_thickbox()
    }
} 

4. Locate the ch9pud_footer_code function and modify the code, adding the following highlighted lines of code to the function body:

function ch9pud_footer_code() {
    // Only load scripts if keyword is found on page
    global $load_scripts;
    if ( $load_scripts ) { ?>
 
    <script type="text/javascript"> 
        jQuery( document ).ready( function() { 
            setTimeout( 
                function(){ 
                    tb_show( 'Pop-Up Message', 
                        '<?php echo plugins_url( 
                        'content.html?width=420&height=220', 
                        __FILE__ ); ?>', null ); 
                }, 2000 ); 
        }); 
    </script> 
     
<?php }  
} 

5. Add the following line of code to register a function that will filter post and page contents before any other parsing and formatting is performed:

add_filter( 'the_posts',
            'ch9pud_conditionally_add_scripts_and_styles' ); 

6. Append the following block of code to provide an implementation for the
   ch9pud_conditionally_add_scripts_and_styles function:

function ch9pud_conditionally_add_scripts_and_styles( $posts ) { 
    // Exit function immediately if no posts are present 
    if ( empty( $posts ) ) {
        return $posts;
    }
 
    // Global variable to indicate if scripts should be loaded 
    global $load_scripts; 
    $load_scripts = false; 
 
    // Cycle through posts and set flag true if 
    // keyword is found 
    foreach ( $posts as $post ) {         
        $shortcode_pos = stripos( $post->post_content, 
                                  '[popup]', 0 ); 
        if ( $shortcode_pos !== false ) { 
            $load_scripts = true; 
            return $posts; 
        } 
    } 
 
    // Return posts array unchanged 
    return $posts;     
} 

7. Insert the following function call to declare a new shortcode along with a function responsible for replacing it with content:

add_shortcode( 'popup', 'ch9pud_popup_shortcode' ); 

8. Add the following code block to provide a simple implementation for the ch9pud_popup_shortcode function:

function ch9pud_popup_shortcode() { 
    return;     
} 

9. Save and close the plugin file.
10. Visit the website's front page and you will notice that the pop-up dialog is no longer displayed.
11. Create a new page and insert the [popup] shortcode in the page contents.
12. View the new page to see that the new pop-up dialog appears, while the [popup] shortcode is not shown.