Move Free Gift to Top

fkcart_move_free_gift_top.php

add_action( 'woocommerce_before_calculate_totals', function ( $cart ) {
	if ( ! $cart instanceof WC_Cart || $cart->is_empty() ) {
		return;
	}

	$contents = $cart->cart_contents;
	if ( count( $contents ) < 2 ) {
		return;
	}

	$rewards = [];
	$rest    = [];

	foreach ( $contents as $key => $item ) {
		$is_reward = ! empty( $item['_fkcart_free_gift'] );

		if ( ! $is_reward && isset( $item['data'] ) && is_object( $item['data'] ) ) {
			$price = (float) $item['data']->get_price();
			if ( 0.0 === $price ) {
				$is_reward = true;
			}
		}

		if ( $is_reward ) {
			$rewards[ $key ] = $item;
		} else {
			$rest[ $key ] = $item;
		}
	}

	if ( empty( $rewards ) ) {
		return;
	}

	$reordered = $rewards + $rest;

	if ( array_keys( $reordered ) === array_keys( $contents ) ) {
		return;
	}

	$cart->cart_contents = $reordered;
}, 99, 1 );