1. Navigate to the ch6-book-review-user-submission directory of the WordPress plugin folder of your development installation.
2. Open the file ch6-book-review-user-submission.php in a text editor.
3. Add the following line of code to register a function that will intercept user-submitted book reviews:

add_action( 'template_redirect', 
            'ch6_brus_match_new_book_reviews' ); 

4. Add the following block of code to implement the ch6_brus_match_new_book_reviews function:

function ch6_brus_match_new_book_reviews( $template ) { 
    if ( !empty( $_POST['ch6_brus_user_book_review'] ) ) { 
        ch6_brus_process_user_book_reviews(); 
    } else { 
        return $template; 
    } 
} 

5. Insert the following code to provide an implementation for the ch6_brus_process_user_book_reviews:

function ch6_brus_process_user_book_reviews() { 
    // Check that all required fields are present and non-empty 
    if ( wp_verify_nonce( $_POST['br_user_form'], 
                          'add_review_form' ) && 
         !empty( $_POST['book_title'] ) && 
         !empty( $_POST['book_author'] ) && 
         !empty( $_POST['book_review_text'] ) &&  
         !empty( $_POST['book_review_book_type'] ) && 
         !empty( $_POST['book_review_rating'] ) ) { 
        // Create array with received data 
        $new_book_review_data = array( 
            'post_status' => 'publish',  
            'post_title' => $_POST['book_title'], 
            'post_type' => 'book_reviews', 
            'post_content' => $_POST['book_review_text'] ); 
 
        // Insert new post in website database 
        // Store new post ID from return value in variable 
        $new_book_review_id =  
                         wp_insert_post( $new_book_review_data ); 
 
        // Store book author and rating 
        add_post_meta( $new_book_review_id, 'book_author', 
                     wp_kses( $_POST['book_author'], array() ) ); 
        add_post_meta( $new_book_review_id, 'book_rating', 
                       (int) $_POST['book_review_rating'] ); 
 
        // Set book type on post 
        if ( term_exists( $_POST['book_review_book_type'], 
                          'book_reviews_book_type' ) ) { 
            wp_set_post_terms( $new_book_review_id, 
                               $_POST['book_review_book_type'], 
                               'book_reviews_book_type' );  
        } 
        // Redirect browser to book review submission page 
        $redirect_address = 
             ( empty( $_POST['_wp_http_referer'] ) ? site_url() : 
                                    $_POST['_wp_http_referer'] ); 
        wp_redirect( add_query_arg( 'add_review_message', '1', 
                     $redirect_address ) ); 
        exit; 
    } else { 
        // Display message if any required fields are missing 
        $abort_message = 'Some fields were left empty. Please '; 
        $abort_message .= 'go back and complete the form.'; 
        wp_die( $abort_message ); 
        exit; 
    } 
} 

6. In the original ch6_brus_book_review_form function, add the following code after the wp_nonce_field function call:

<?php if ( isset( $_GET['add_review_message'] ) 
            && $_GET['add_review_message'] == 1 ) { ?> 
 
    <div style="margin: 8px;border: 1px solid #ddd; 
        background-color: #ff0;"> 
    Thank for your submission! 
    </div> 
 
<?php } ?> 
 
<!-- Post variable to indicate user-submitted items --> 
<input type="hidden" name="ch6_brus_user_book_review" value="1" /> 

7. Save and close the plugin file.
8. Go back to the book review submission form and submit a review to send all the fields to the newly created processing function. After processing the new content, the script will return to the form, which will display a confirmation message.