WordPress – source link plugin – how to modify it?

by

You can add the extra (link/URL label) field like so:

  1. In the wpse_source_meta_box() function, add the (HTML of the) extra field:

    echo '<input type="text" id="source-link-label"" name="source_link_label" value="'.
  get_post_meta( $post->ID, '_source_link_label', true ) .'" size="25" />';

    so as you can see, the field name is _source_link_label as used in the get_post_meta() call when retrieving the field value.

    However, since there are now two fields, you may want to add a placeholder to the input fields:

      echo '<input type="text" id="source-link"" name="source_link" value="'.
    get_post_meta( $post->ID, '_source_link', true ) .'" size="25" placeholder="URL" />';

  echo '<input type="text" id="source-link-label"" name="source_link_label" value="'.
    get_post_meta( $post->ID, '_source_link_label', true ) .'" size="25" placeholder="Label" />';

    Or add a <label> before the fields:

      echo '<label for="source-link">URL:</label> ';
  echo '<input type="text" id="source-link"" name="source_link" value="'.
    get_post_meta( $post->ID, '_source_link', true ) .'" size="25" />';

  echo '<label for="source-link-label">Label:</label> ';
  echo '<input type="text" id="source-link-label"" name="source_link_label" value="'.
    get_post_meta( $post->ID, '_source_link_label', true ) .'" size="25" />';

  2. In the wpse_source_link_save() function, save/update the field value like so:

    update_post_meta( $post_id, '_source_link_label', $_POST['source_link_label'] );

  3. And then use the field value (or the link label) along with the link URL, like so:

    <?php
// Show if the source link was specified.
if ( $url = get_post_meta( $post->ID, '_source_link', true ) ) :
    $label = get_post_meta( $post->ID, '_source_link_label', true );
    $label = $label ? $label : $url;
?>
    <div class="source-link">
        Source: <a href="https://wordpress.stackexchange.com/questions/320902/<?php echo esc_url( $url ); ?>"><?php // wrapped (for clarity)
          echo esc_html( $label ); ?></a>
    </div>
<?php endif; // end $url ?>

    (Part of the code was taken from here.)

So the full code, without the step #3’s part, would look like this. 🙂

That should work, but I suggest you to use sanitize_text_field() when updating the fields:

update_post_meta( $post_id, '_source_link', sanitize_text_field( $_POST['source_link'] ) );
update_post_meta( $post_id, '_source_link_label', sanitize_text_field( $_POST['source_link_label'] ) );

See this article for more details on that.

UPDATE

You can use this code in place of what I gave in step #3 above, to make sure the source link is only shown on the last page of a multi-page content (split using <!--nextpage-->) — the link (if set) would always be shown on the first page if the content is not set to multi-page:

<?php
global $post, $pages, $page;

$total = count( $pages );
// Show if there's only one page, or that we're on the last page.
if ( $total < 2 || $page === $total ) :
    // Show if the source link was specified.
    if ( $url = get_post_meta( $post->ID, '_source_link', true ) ) :
        $label = get_post_meta( $post->ID, '_source_link_label', true );
        $label = $label ? $label : $url;
    ?>
        <div class="source-link">
            Source: <a href="https://wordpress.stackexchange.com/questions/320902/<?php echo esc_url( $url ); ?>"><?php
              echo esc_html( $label ); ?></a>
        </div>
    <?php endif; // end $url
endif; // end last page check
?>