woocommerce_before_checkout_form │ action-hook │ WC 1.0

Usage

add_action( 'woocommerce_before_checkout_form', 'wp_kama_woocommerce_before_checkout_form_action' );

/**
 * Function for `woocommerce_before_checkout_form` action-hook.
 * 
 * @param  $checkout 
 *
 * @return void
 */
function wp_kama_woocommerce_before_checkout_form_action( $checkout ){

	// action...
}

$checkout

-

Where the hook is called

do_action( 'woocommerce_before_checkout_form', $checkout );

Where the hook is used in WooCommerce

add_action( 'woocommerce_before_checkout_form', 'woocommerce_checkout_login_form', 10 );

add_action( 'woocommerce_before_checkout_form', 'woocommerce_checkout_coupon_form', 10 );

add_action( 'woocommerce_before_checkout_form', 'woocommerce_output_all_notices', 10 );