register_post_meta() │ WP 4.9.8

Registers a meta key for posts (post custom field).

It is a wrapper for the register_meta function for easy registration of post meta-fields.

To do the same for taxonomy, see register_term_meta().

The registered meta fields are stored in the global $wp_meta_keys array.

Uses: register_meta()
1 time — 0.000126 sec (fast) | 50000 times — 0.27 sec (very fast) | PHP 7.1.11, WP 4.9.8

No Hooks.

Return

true|false. True if the meta key was successfully registered, false if not.

Usage

register_post_meta( $post_type, $meta_key, $args );
$post_type(string) (required)
Post type to register a meta key for. Pass an empty string to register the meta key across all existing post types.
$meta_key(string) (required)
The meta key to register.
$args(array) (required)
Data used to describe the meta key when registered. See register_meta() for a list of supported arguments.

#1 Register a meta-field for pages only

register_post_meta( 'page', 'my_meta_key', array(
	// Add to REST response
	'show_in_rest' => true,
	// Process the value of the field when saving it to the database, function absint()
	'sanitize_callback' => 'absint',
) );

Now the meta-field with the key my_meta_key will be registered for pages only.

The same can be done with register_meta(), like this:

register_meta( 'post', 'my_meta_key', array(
	'object_subtype' => 'page', // post type
	'show_in_rest' => true,
	'sanitize_callback' => 'absint',
) );

#2 More examples

See the register_meta() function for more examples and usage features.

Changelog

Since 4.9.8 Introduced.

Code of register_post_meta() WP 6.0.1

wp-includes/post.php 
function register_post_meta( $post_type, $meta_key, array $args ) {
	$args['object_subtype'] = $post_type;

	return register_meta( 'post', $meta_key, $args );
}

WP extension (enhancement)

Metadatas (any)