WordPress Plugin Development Cookbook - Second Edition

How to do it...

1. Navigate to the ch5-post-source-link folder of the WordPress plugin directory of your development installation.
2. Open the ch5-post-source-link.php file in a code editor.
3. Add the following line of code to register a filter function to be called when the post and page content is prepared for display:

add_filter( 'the_content', 'ch5_psl_display_source_link' );

4. Add the following code section to provide an implementation for the ch5_psl_display_source_link function:

function ch5_psl_display_source_link ( $content ) {     $post_id = get_the_ID();     if ( !empty( $post_id ) ) {        if ( 'post' == get_post_type( $post_id ) ||             'page' == get_post_type( $post_id ) ) {            // Retrieve current source name and address for post  $post_source_name ...