Create post meta box in wordpress

WordPress meta box is a very useful feature that allows you to add completely custom data to posts or pages in WordPress. Custom meta box contains data which allow admin to add/edit/delete post metadata. We can add any number of meta boxes to posts and pages on the WordPress admin side. Below is the best explanation for how to create post meta box in WordPress.

Custom meta box is the way where you can add an additional piece of data into your posts and pages. This data should be related to the main post. However, to understand how to custom meta boxes are useful for that you must understand how to add, update, delete and display post metadata.

For example, if you want to display testimonial listing and you want to add designation field with the testimonial post for that you need to add custom meta box for designation field.

Below are the functions for add, update, delete and display the meta box in WordPress.

• add_post_meta()
• update_post_meta()
• delete_post_meta()
• get_post_meta()

add_meta_box( string $id, string $title, callable $callback, string|array|WP_Screen screen = null, string $context = ‘advanced’, string $$priority = ‘default’, array $callback_args = null )

$id :- (string)(reuqired) ID for meta box.

$title :- (string)(reuqired) Meta box title.

$callback :- (callable)(reuqired) Funcion that fill the meta box with the content and the function should echo it’s output.

$screen :- (string|array)(optional) Screen in which to show meta box.

$context :- (string)(optional) The context within the screen where the box should be display.

$priority :- (string)(optional) The priority within the context where the box should show (‘low’ and ‘high’).

$callback_args :- (array)(optional) Data that should be set as $args property of the box array.

update_meta_box( $post_id, $meta_key, $meta_value, $prev_value )

$post_id :- (integer)(required) The ID of the post which you want to edit.

$meta_key :- (string)(required) The key of the custom field that you want to edit.

$meta_value :- (mixed)(required) The new value of the custom field.

$prev_value :- (mixed)(optional) The old value of the custom field that you want to change.

delete_meta_box( $post_id, $meta_key, $meta_value )

$post_id :- (integer)(required) The ID of the post which you want to delete.

$meta_key :- (string)(required) The key of the custom field that you want to delete.

$meta_value :- (mixed)(optional) The value of the field that you will delete.

get_meta_box( int $post_id, string $key = ‘ ‘, bool $single = false )

$post_id :- (integer)(required) The ID of the post.

$key :- (string)(optional) The meta key for retrive data.

$single :- (bool)(optional) Whether to return single value or not.

Below is the code for creating a custom meta boxes. For that, you need to add below code in a functions.php file of your current theme.

/**
 * Add custom metabox
 */
function Helpyouforever_add_metabox()
{
    $screen = 'movies';
    add_meta_box('demo_text','Extra Content','Helpyouforever_display_metabox', $screen, 'normal', 'high');
}
add_action( 'add_meta_boxes', 'Helpyouforever_add_metabox' ) ;

/**
 * Display PostMeta
 * @global type $wbdb
 * @param type $post
 */
function Helpyouforever_display_metabox($post)
{
    global $wbdb;
    $sample_text = 'sample_text';
    $get_display_text = get_post_meta( $post->ID,$sample_text, true );  
    ?>
    <label for="sample_text">Sample Text : </label>
        <input type="text" name="sample_text" id="sample_text" value="<?php echo $get_display_text;?>" />
    <?php
}

/**
 * Save Post Meta
 * @param type $post
 */
function Helpyouforever_save_metabox($post)
{
    $sample_text = $_POST['sample_text'];
    update_post_meta(  $post, 'sample_text', $sample_text);
}
add_action('save_post','Helpyouforever_save_metabox');

After adding this code then you can see meta box option in your post as you given post type in the above code. below is the screenshot for meta box display in the post.