(hook_prefix)purchase_note │ filter-hook │ WC 1.0

Usage

add_filter( '(hook_prefix)purchase_note', 'wp_kama_hook_prefixpurchase_note_filter', 10, 2 );

/**
 * Function for `(hook_prefix)purchase_note` filter-hook.
 * 
 * @param  $parent_data_purchase_note 
 * @param  $that                      
 *
 * @return 
 */
function wp_kama_hook_prefixpurchase_note_filter( $parent_data_purchase_note, $that ){

	// filter...
	return $parent_data_purchase_note;
}

$parent_data_purchase_note

-

$that

-

Where the hook is called

$value = apply_filters( $this->get_hook_prefix() . 'purchase_note', $this->parent_data['purchase_note'], $this );

Where the hook is used in WooCommerce