WordPress Version: 4.3
/**
* Add meta data field to a user.
*
* Post meta data is called "Custom Fields" on the Administration Screens.
*
* @since 3.0.0
* @link https://codex.wordpress.org/Function_Reference/add_user_meta
*
* @param int $user_id User ID.
* @param string $meta_key Metadata name.
* @param mixed $meta_value Metadata value.
* @param bool $unique Optional, default is false. Whether the same key should not be added.
* @return int|false Meta ID on success, false on failure.
*/
function add_user_meta($user_id, $meta_key, $meta_value, $unique = false)
{
return add_metadata('user', $user_id, $meta_key, $meta_value, $unique);
}