The add_{$meta_type}_meta WordPress PHP action fires immediately before meta of a specific type is added. The dynamic portion of the hook name, $meta_type, refers to the meta object type (post, comment, term, user, or any other type with an associated meta table).
Usage
add_action('add_post_meta', 'your_custom_function', 10, 3);
function your_custom_function($object_id, $meta_key, $_meta_value) {
// your custom code here
}
Parameters
- $object_id (int): ID of the object metadata is for.
- $meta_key (string): Metadata key.
- $_meta_value (mixed): Metadata value.
More information
See WordPress Developer Resources: add_{$meta_type}_meta
Examples
Validate post meta before adding
Check if the meta key is ‘price’ and ensure the value is a positive number before adding.
add_action('add_post_meta', 'validate_price_meta', 10, 3);
function validate_price_meta($object_id, $meta_key, $_meta_value) {
if ($meta_key === 'price' && (!is_numeric($_meta_value) || $_meta_value < 0)) {
return false;
}
}
Log added post meta
Log added post meta to a custom log file.
add_action('add_post_meta', 'log_added_post_meta', 10, 3);
function log_added_post_meta($object_id, $meta_key, $_meta_value) {
error_log("Added meta: {$meta_key} => {$_meta_value} for post {$object_id}", 3, '/path/to/your_log_file.log');
}
Set default post thumbnail
Set a default post thumbnail when a new post is created and no featured image is set.
add_action('add_post_meta', 'set_default_thumbnail', 10, 3);
function set_default_thumbnail($object_id, $meta_key, $_meta_value) {
if ($meta_key === '_thumbnail_id' && empty($_meta_value)) {
update_post_meta($object_id, '_thumbnail_id', 'your_default_thumbnail_id');
}
}
Sanitize user meta
Sanitize user meta data before it is added to the database.
add_action('add_user_meta', 'sanitize_user_meta', 10, 3);
function sanitize_user_meta($object_id, $meta_key, $_meta_value) {
if ($meta_key === 'custom_user_data') {
$_meta_value = sanitize_text_field($_meta_value);
}
}
Add custom term meta
Add custom term meta data for a new term.
add_action('add_term_meta', 'add_custom_term_meta', 10, 3);
function add_custom_term_meta($object_id, $meta_key, $_meta_value) {
if ($meta_key === 'custom_term_data') {
$_meta_value = 'your_custom_data';
}
}