Day 8: Custom Meta Boxes

A meta box is a draggable box shown on a post edit page, usually on sidebar. Category box, tags box are some of the in-built meta boxes. A meta box can be used to select or enter any information additional to the post. Let’s say you have a custom post type book. You can create a custom meta box your CPT book which will take input as author’s name, publisher, price, year, etc and save this information in wp_postmeta table.

Creating a meta box requires three steps:

• Creating the box itself,
• Define content of meta box,
• How to handle input data from box.

Defining Meta Box and the content

add_action('add_meta_boxes', 'book_meta_box');
function book_meta_box(){
    add_meta_box(
        'book_info_box',
        'Book Information',
        'book_box_content,
        'book',
        'side'
    );
}

function book_box_content($post){
    echo '<label for="price"> Price </label>';
    echo '<input type="text" id="price" name="price" placeholder="Enter price" />';
}

Handling/saving input data

add_action('save_post', 'save_book_info');
function save_book_info($post_id, $post) {
    /* Verify the nonce before proceeding. */

    /* Get the post type object. */
    $post_type = get_post_type_object( $post->post_type );

    /* Check if the current user has permission to edit the post. */
    if ( !current_user_can( $post_type->cap->edit_post, $post_id))
        return $post_id;

    $book_price = $_POST['price'];
    update_post_meta( $post_id, 'book_price', $book_price );
}

Following are the frequently used functions for post meta:

• add_post_meta(): Adds post metadata.
• update_post_meta(): Updates post metadata.
• delete_post_meta(): Deletes post metadata.
• get_post_meta(): Retrieves post metadata.