Function: get_post_meta

Related Categories for Pages

Just whipped this up as a demo for someone, and thought it would make a great addition here as well.

The idea was to be able to link a category to a page. So if you have a page about Beavers, you can link it to your blog category called Beaver News.

This code is almost a plugin – it will work with some tweaking, but won’t do anything out-of-the-box.

It adds a category selection dropdown to the Edit Page screen, and saves the value as meta. (As-is, you aren’t allowed to not select a category, with a little hacking that should be fixable).

The code at the end includes a demo of how you might use this page meta on the frontend. This code, however, only outputs it in a meta box on the Edit Page screen.

add_action('add_meta_boxes', 'create_box' );
function create_box() {
    add_meta_box( 'related_category', 'Related Category', 'box_html', 'page', 'side');
}

function box_html() {
    global $post;
    $selected = get_post_meta( $post->ID, '_related_category', true );
    wp_nonce_field( plugin_basename(__FILE__), 'related_cat_nonce' );
    wp_dropdown_categories( array('hide_empty' => false, 'show_count' => true, 'name' => 'related_cat', 'selected' => $selected ) );
}

add_action('save_post', 'save_box' );
function save_box( $post_id ) {

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

    if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) 
        return $post_id;

    if ( 'page' == $_POST['post_type'] && !current_user_can( 'edit_page', $post_id ) )
        return $post_id;
    
    if (!isset($_POST['related_cat']))
        return $post_id;
    else {
        $related_cat = $_POST['related_cat'];
        update_post_meta( $post_id, '_related_category', $related_cat, get_post_meta( $post_id, '_related_category', true ) );
    }
    
}

// this just puts the feed in a meta box on the appropriate page
// it can be ripped out and added to the page template
add_action('add_meta_boxes', 'create_box_display' );
function create_box_display() {
    add_meta_box( 'related_category_display', 'Related Category Display', 'box_html_display', 'page', 'side');
}

function box_html_display() {
    global $post;
    $selected = get_post_meta( $post->ID, '_related_category', true );
    $related = get_posts('numberposts=5&category='.$selected);
    foreach($related as $p) {
        echo '<h4>'.$p->post_title.'</h4>';
        echo wpautop($p->post_content);
        echo '<hr />';
    }
}

Use a Custom Field to Add to the

I needed a very simple way to custom styles or scripts to the <head>, and I didn’t really want to customize the theme.

add_action( 'wp_head', 'wp_head_custom_field' );
function wp_head_custom_field() {
    if ( is_single() ) {
        global $post;
        $html = get_post_meta( $post->ID, 'wp_head', true );
        echo $html;
    }
}

With this, I just needed to add my pre-formatted javascript or css to a custom field called ‘wp_head’ and it would then be added to the <head> just like I needed. I added the is_single() as a precaution.

Add Post Options To “Publish” Meta Box

We often add custom meta boxes to a page or post in order to save specific kinds of data. In some cases, the best place to add those fields really isn’t in some box that gets added to the end of the page. The option needs to be in a bit more prominent location.

Fortunately, it’s possible to add text or form elements to the “Publish” meta box.

add_action( 'post_submitbox_misc_actions', 'article_or_box' );
add_action( 'save_post', 'save_article_or_box' );
function article_or_box() {
    global $post;
    if (get_post_type($post) == 'post') {
        echo '<div class="misc-pub-section misc-pub-section-last" style="border-top: 1px solid #eee;">';
        wp_nonce_field( plugin_basename(__FILE__), 'article_or_box_nonce' );
        $val = get_post_meta( $post->ID, '_article_or_box', true ) ? get_post_meta( $post->ID, '_article_or_box', true ) : 'article';
        echo '<input type="radio" name="article_or_box" id="article_or_box-article" value="article" '.checked($val,'article',false).' /> <label for="article_or_box-article" class="select-it">Article</label><br />';
        echo '<input type="radio" name="article_or_box" id="article_or_box-box" value="box" '.checked($val,'box',false).'/> <label for="article_or_box-box" class="select-it">Box</label>';
        echo '</div>';
    }
}
function save_article_or_box($post_id) {

    if (!isset($_POST['post_type']) )
        return $post_id;

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

    if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) 
        return $post_id;

    if ( 'post' == $_POST['post_type'] && !current_user_can( 'edit_post', $post_id ) )
        return $post_id;
    
    if (!isset($_POST['article_or_box']))
        return $post_id;
    else {
        $mydata = $_POST['article_or_box'];
        update_post_meta( $post_id, '_article_or_box', $_POST['article_or_box'], get_post_meta( $post_id, '_article_or_box', true ) );
    }

}

What I needed at one time was a way to mark a post that would determine whether it would be displayed in a regular article style, or in a special box style. Nowadays, I can use post formats. But the point is, you could put other options there. Perhaps an expiration date field.

Shortcode with Content

Here’s a bit of code that will allow you to add a footnote to your post – inline. It’s easy enough to add footnotes manually, sure. But where’s the fun in that?

add_shortcode( 'footnote', 'footnote_shortcode' );
function footnote_shortcode( $atts, $content ) {
	extract(shortcode_atts( array() , $atts));
	global $post;
    update_post_meta( $post->ID, '_footnote', $content, get_post_meta( $post->ID, '_footnote', true ) );
	return ' <a href="#fn_'.$post->ID.'">*</a> ';
}
add_filter( 'the_content', 'append_footnote' ); 
function append_footnote($content) {
	global $post;
	if ( get_post_meta( $post->ID, '_footnote', true ) != '' )
	$content .= '<p id="fn_'.$post->ID.'">* '.get_post_meta( $post->ID, '_footnote', true ) .'</p>';
	
	return $content;
}

A footnote could then be added like this:

The moon is 384,403 km [footnote]238,857 miles[/footnote] from the earth.

There might be a better way to append the footnote to the end – so feel free to investigate and improve.