(hook_prefix)length │ filter-hook │ WC 1.0

Usage

add_filter( '(hook_prefix)length', 'wp_kama_hook_prefixlength_filter', 10, 2 );

/**
 * Function for `(hook_prefix)length` filter-hook.
 * 
 * @param  $parent_data_length 
 * @param  $that               
 *
 * @return 
 */
function wp_kama_hook_prefixlength_filter( $parent_data_length, $that ){

	// filter...
	return $parent_data_length;
}

$parent_data_length

-

$that

-

Where the hook is called

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

Where the hook is used in WooCommerce