How to add Custom Admin Meta Boxes to a WordPress Custom Post Type

I decided to write this detailed tutorial on how to add custom field meta boxes to the WordPress admin mostly because I couldn’t find a decent description of how to do it anywhere online. Hopefully this will help others having trouble trying to learn how to add admin meta boxes with custom fields for a custom post type in WordPress. It is an essential step to learning WordPress plugin development.

Let’s dive in and learn some code because I believe that is the quickest and easiest way to learn this advanced WordPress method. I say it is an advanced subject because it is a little complex for beginners. If you are not sure how to start your own plugin yet in WordPress, then this topic may be too advanced for you. You should at least learn how to make a very basic WordPress plugin first, so feel free to read one of my more basic WordPress plugin tutorials first.

First of all, I’ll show you how to add a single meta box with a single field in it. It is also important to know that you can have more than one field inside a single meta box. It is equally important to know that you can have more than one meta box. Each meta box can have one or more fields in them. It just depends on your individual needs. Below is the basic code for how to add a custom post type with a custom field inside of an admin meta box. I’ll also include a basic plugin heading so you may follow along and create a working example to work from:

Adding a Custom Post Type to WordPress Plugin

<?php
/**
 * Plugin Name: Jafty Metabox Example Plugin
 * Plugin URI: http://jafty.com/blog/crash-course-on-wordpress-plugin-development/
 * Description: A Plugin that adds metaboxes to your WordPress blog or site.
 * Version: 1.0
 * Author: Ian L. of Jafty.com
 * Author URI: http://jafty.com
 * License: GPL2
 */
 

 //Add new Custom Post Type named videos:
add_action(‘init’, ‘create_video_posttype’);
function create_video_posttype(){
    register_post_type(‘videos’,
        array(
            ‘labels’ => array(
            ‘name’ => __(‘Videos’),
            ‘singular_name’ => __(‘Video’)
            ),
        ‘public’ => true,
        ‘has_archive’ => true,
        ‘rewrite’ => array(‘slug’ => ‘video’),
        )
    );
}//end create_video_posttype function

?>

Okay, now start a .php file and add the above code in green to the start of it. Name the file “jafty-metabox-example-plugin.php” and save it. Please NOTE: it is important to go into wp-admin/settings/permalinks and re-save those settings after activating a plugin with a custom post type or after adding a custom post type to a plugin. If you do not do this, the custom post type posts will not show up on the front end of your blog.

At this point, you should be able to upload the jafty-metabox-example-plugin.php file to your WordPress site’s plugins folder and activate it. If it works, you’ll see a new “Video” option in the left navigation menu of wp-admin as in the following photo:

videoCPT

Add a Metabox with a Custom Field to your CPT

Now here is the code to add to the end of the file you started above(just before the closing PHP tag) that will add a meta-box with a custom field inside of it to your plugin. It adds a field to the wp-admin edit screen for the videos CPT(custom post type):

//Add custom admin Meta Boxes:
add_action(‘add_meta_boxes’, ‘add_ians_metaboxes’);
function add_ians_metaboxes(){
//add meta box for Video type and description:
add_meta_box(‘meta_box_html_id’, ‘Video Details’, ‘video_details_function’, ‘videos’, ‘normal’, ‘high’);
}

//##################### Video Details Metabox: ################
function video_details_function() {
global $post;  
//Noncename needed to verify where the data originated
echo ‘<input type=”hidden” name=”eventmeta_noncename” id=”eventmeta_noncename” value=”‘ .
wp_create_nonce(plugin_basename(__FILE__)) . ‘” />’;

//Get video description data if its already been entered
$video_desc = get_post_meta($post->ID, ‘_video_desc’, true);
    
//Start video Description text field HTML:
?>
Video Description:
<input type=”text” name=”video_desc” value=”<?php echo $video_desc; ?>” class=”widefat” />
<?php
}//end video_details_function

Save the “jafty-metabox-example-plugin.php” file and update it on your site and click on the “Video” link in wp-admin and then click on “Add New” to see the add/edit screen for your new CPT. You will notice your  custom meta-box with the heading of “Video Details”. You will also notice the meta-box contains a custom field named “Video Description”. You can see both near the bottom of the photo below:

customField

Saving Custom Field Data

Your not quite done however. While the code above will display the metaboxes, it does not save the data as I soon discovered. To save the data, you’ll need to add this code directly after your video_details callback function:

//hook into save_post to save the meta box data:
add_action (‘save_post’, ‘save_video_desc’);

function save_video_desc($post_id) {
//verify the metadata is set
     if (isset( $_POST[‘video_desc’])) {
     //save the metadata
     update_post_meta ($post_id, ‘_video_desc’, strip_tags($_POST[‘video_desc’]));
     }
}

 

 Adding Multiple Meta-Boxes and Custom Fields

Next I’ll show you what our final plugin file would look like if we were to add another custom field to our meta-box and then another meta-box with yet another custom field inside of it. This way you can see how more than one meta-box is added and also how to add more than one field inside of a single meta-box. Here is the complete plugin code containing a total of two meta-boxes and three total custom fields:

<?php
/**
* Plugin Name: Jafty Metabox Example Plugin
* Plugin URI: http://jafty.com/blog/crash-course-on-wordpress-plugin-development/
* Description: A Plugin that adds metaboxes to your WordPress blog or site.
* Version: 1.0
* Author: Ian L. of Jafty.com
* Author URI: http://jafty.com
* License: GPL2
*/

//Add new Custom Post Type named videos:
add_action(‘init’, ‘create_video_posttype’);
function create_video_posttype(){
register_post_type(‘videos’,
array(
‘labels’ => array(
‘name’ => __(‘Videos’),
‘singular_name’ => __(‘Video’)
),
‘public’ => true,
‘has_archive’ => true,
‘rewrite’ => array(‘slug’ => ‘video’),
)
);
}//end create_video_posttype function

//Add custom admin Meta Boxes:
add_action(‘add_meta_boxes’, ‘add_ians_metaboxes’);
function add_ians_metaboxes(){
//add the first meta box for Video type and description:
add_meta_box(‘meta_box_html_id’, ‘Video Details’, ‘video_details_function’, ‘videos’, ‘normal’, ‘high’);
//add a second meta box for Video Rating
add_meta_box(‘meta_box_html_id2’, ‘Video Rating’, ‘video_rating_function’, ‘videos’, ‘normal’, ‘high’);
}
//################## Video Details Metabox: ####################
function video_details_function() {
global $post;

//Noncename needed to verify where the data originated
echo ‘<input type=”hidden” name=”eventmeta_noncename” id=”eventmeta_noncename” value=”‘ .
wp_create_nonce(plugin_basename(__FILE__)) . ‘” />’;

//Get the video type  if its already been entered
$video_type = get_post_meta($post->ID, ‘_video_type’, true);
// Get the video description if its already been entered
$video_desc = get_post_meta($post->ID, ‘_video_desc’, true);

//Start type select field HTML:
?>
Video Type: <select name=”video_type”>
<option value=”DVD”<?php if($video_type==”DVD”)echo ” selected”;?>>DVD<option>
<option value=”Blueray”<?php if($video_type==”Blueray”)echo ” selected”;?>>Blueray<option>
</select><br />
<?php
// Start video description field HTML:
?>
Video Description:
<input type=”text” name=”_location” value=”<?php echo $video_desc; ?>” class=”widefat” />
<?php
}//end video_details_function
//##################### Video Rating Metabox: ###################
function video_rating_function() {
global $post;

//Noncename needed to verify where the data originated
echo ‘<input type=”hidden” name=”eventmeta_noncename” id=”eventmeta_noncename” value=”‘ .
wp_create_nonce(plugin_basename(__FILE__)) . ‘” />’;

//Get the start_month data if its already been entered
$video_rating = get_post_meta($post->ID, ‘_video_rating’, true);

//Start type select field HTML:
?>
Video Type: <select name=”_video_rating”>
<option value=”R”<?php if($video_rating==”R”)echo ” selected”;?>>R<option>
<option value=”PG”<?php if($video_rating==”PG”)echo ” selected”;?>>PG<option>
</select><br />
<?php
}//end video_rating_function
?>

//add your save data hook and function to save all fields here:

//hook into save_post to save the meta box data:
add_action (‘save_post’, ‘save_video_data’);

function save_video_data($post_id) {
//verify the metadata is set
     if (isset( $_POST[‘video_desc’])) {
     //save the metadata
     update_post_meta ($post_id, ‘_video_type’, strip_tags($_POST[‘video_type’]));

    update_post_meta ($post_id, ‘_video_desc’, strip_tags($_POST[‘video_desc’]));

    update_post_meta ($post_id, ‘_video_rating, strip_tags($_POST[‘video_rating’]));
     }
}

That’s it! Save the above code in a PHP file and name it the same name as before and allow it to overwrite the original plugin file if you were following along and it will add another meta-box and a couple more custom fields to your custom post type. Now you should have enough information to be able to make your own custom admin meta-boxes and fields for your next WordPress plugin or theme. Here is an image of the two meta-boxes from when I tested the above code myself:

metaboxes

Summary

Now you should know more than enough to make your own plugin or custom theme with its own admin meta-boxes and custom fields for any custom post types you may have. It is important to know that you can also use any other type of form element in the above examples. Feel free to experiment and use textareas, radio buttons, checkboxes etc in your own code.

 

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