Adding Metaboxes – so much code is there a shorter DRY way?

I added the following two metaboxes to my functions.php file and it works, but it’s a lot of code.

Question: Is there a shorter or simple way to do this without a plugin?

/**
 * Add custom fields to a specific WP page template & save it
*/

$post_id = $_GET['post'] ? $_GET['post'] : $_POST['post_ID'] ;
$template_file = get_post_meta($post_id,'_wp_page_template',TRUE);
  // check for a template type
  if ($template_file == 'template-testhome.php') { //this is the template change on real site

  // add the actions to add functions :: how many slides to show
   add_action( 'admin_menu', 'slidestoshow_create_post_meta_box' );
   add_action( 'save_post', 'slidestoshow_save_post_meta_box', 10, 2 );
   

  // add the actions to add functions :: type of slider infinite or not
   add_action( 'admin_menu', 'slidetype_create_post_meta_box' );
   add_action( 'save_post', 'slidetype_save_post_meta_box', 10, 2 );


//begin slides to show meta box
function slidestoshow_create_post_meta_box() {
    add_meta_box( 'slidestoshow_meta_box', 'Slides to Show & Scroll (1-6)', 'slidestoshow_page_meta_box', 'page', 'normal', 'high' );
}

function slidestoshow_page_meta_box( $object, $box ) { ?>
    <p>
        <label for="slides-to-show-scroll">Slides to Show & Scroll (1-6)</label>
        <!-- keep reference
        <textarea name="second-excerpt" id="second-excerpt" cols="60" rows="4" tabindex="30" style="width: 97%;"><?php echo wp_specialchars( get_post_meta( $object->ID, 'Second Excerpt', true ), 1 ); ?></textarea>
        -->
       <input type="text" id="slides-to-show-scroll" name="slides-to-show-scroll" value="<?php echo wp_specialchars( get_post_meta( $object->ID, 'Slides to Show Scroll', true ), 1 ); ?>" size="10" />
       <input type="hidden" name="slidestoshow_page_meta_box_nonce" value="<?php echo wp_create_nonce( plugin_basename( __FILE__ ) ); ?>" />
    </p>
<?php }
// end create the meta box for slides to show


//begin slide type meta box
function slidetype_create_post_meta_box() {
    add_meta_box( 'slidetype_meta_box', 'Infinte (true or false)', 'slidetype_page_meta_box', 'page', 'normal', 'high' );
}

function slidetype_page_meta_box( $object, $box ) { ?>
    <p>
        <label for="slide-type">Infinite (true or false)</label>
       <input type="text" id="slide-type" name="slide-type" value="<?php echo wp_specialchars( get_post_meta( $object->ID, 'Slide Type', true ), 1 ); ?>" size="10" />
       <input type="hidden" name="slidetype_page_meta_box_nonce" value="<?php echo wp_create_nonce( plugin_basename( __FILE__ ) ); ?>" />
    </p>
<?php }
// end create the meta box for slides type


function slidestoshow_save_post_meta_box( $post_id, $post ) {

    if ( !wp_verify_nonce( $_POST['slidestoshow_page_meta_box_nonce'], plugin_basename( __FILE__ ) ) )
        return $post_id;

    if ( !current_user_can( 'edit_post', $post_id ) )
        return $post_id;

    $meta_value = get_post_meta( $post_id, 'Slides to Show Scroll', true );
    $new_meta_value = stripslashes( $_POST['slides-to-show-scroll'] );

    if ( $new_meta_value && '' == $meta_value )
        add_post_meta( $post_id, 'Slides to Show Scroll', $new_meta_value, true );

    elseif ( $new_meta_value != $meta_value )
        update_post_meta( $post_id, 'Slides to Show Scroll', $new_meta_value );

    elseif ( '' == $new_meta_value && $meta_value )
        delete_post_meta( $post_id, 'Slides to Show Scroll', $meta_value );
}
//end the save for slides to show



function slidetype_save_post_meta_box( $post_id, $post ) {

    if ( !wp_verify_nonce( $_POST['slidetype_page_meta_box_nonce'], plugin_basename( __FILE__ ) ) )
        return $post_id;

    if ( !current_user_can( 'edit_post', $post_id ) )
        return $post_id;

    $meta_value = get_post_meta( $post_id, 'Slide Type', true );
    $new_meta_value = stripslashes( $_POST['slide-type'] );

    if ( $new_meta_value && '' == $meta_value )
        add_post_meta( $post_id, 'Slide Type', $new_meta_value, true );

    elseif ( $new_meta_value != $meta_value )
        update_post_meta( $post_id, 'Slide Type', $new_meta_value );

    elseif ( '' == $new_meta_value && $meta_value )
        delete_post_meta( $post_id, 'Slide Type', $meta_value );
}
//end the save for slide type

Leverage Functions

You can extract the redundant code into reusable functions. For example, the last two functions could be rewritten like this. My resulting code is actually 2 lines longer, but it’s much cleaner from a debugging standpoint. And, if there were a third custom field, this approach would definitely be shorter.

function slidestoshow_save_post_meta_box( $post_id, $post ) {

    $nonce="slidestoshow_page_meta_box_nonce";
    $meta_label="Slides to Show Scroll";
    $meta_slug = 'slides-to-show-scroll';

    if ( !my_save_post_met_box( $post_id, $post, $meta_label, $meta_slug, $nonce ) ) {
        return $post_id;
    }
}

function slidetype_save_post_meta_box( $post_id, $post ) {

    $nonce="slidetype_page_meta_box_nonce";
    $meta_label="Slide Type";
    $meta_slug = 'slide-type';

    if ( !my_save_post_met_box( $post_id, $post, $meta_label, $meta_slug, $nonce ) ) {
        return $post_id;
    }
}

function my_save_post_meta_box( $post_id, $post, $meta_label, $meta_slug, $nonce ) {

    if ( !wp_verify_nonce( $_POST[$nonce], plugin_basename( __FILE__ ) ) )
        return;

    if ( !current_user_can( 'edit_post', $post_id ) )
        return;

    $meta_value = get_post_meta( $post_id, $meta_label, true );
    $new_meta_value = stripslashes( $_POST[$meta_slug] );

    if ( $new_meta_value && '' == $meta_value )
        add_post_meta( $post_id, $meta_label, $new_meta_value, true );

    elseif ( $new_meta_value != $meta_value )
        update_post_meta( $post_id, $meta_label, $new_meta_value );

    elseif ( '' == $new_meta_value && $meta_value )
        delete_post_meta( $post_id, $meta_label, $meta_value );
}

And, you could reclaim your two lines by renaming your nonce to the same scheme as your slug. Something like this:

if ( !wp_verify_nonce( $_POST[$meta_slug . '_page_meta_box_nonce'], plugin_basename( __FILE__ ) ) )

Use Arrays and Foreach Loops

Your action hooks could be optimized like this. Again, more lines of code–with only two custom fields–but easier to read and debug.

$fnc_labels = array( 'slidestoshow', 'slidetype' );

foreach ( $fnc_labels AS $fnc_label ) {
    add_action( 'admin_menu', $fnc_label . '_create_post_meta_box' );
    add_action( 'save_post', $fnc_label . '_save_post_meta_box', 10, 2 );
}