Setting booking fields data from the URL parameters.

functions.php

<?php

/**
 * Setting booking fields data from the URL parameters. start and end date is passed in the URL parameters. This can be changed according to business requirements. e.g check_in and check_out.
 */
function bkap_set_bookings_via_get() {

	if ( isset( $_GET['start'] ) && isset( $_GET['end'] ) ) {

		$start_date = $_GET['start'];
		if ( ! empty( $_GET['end'] ) ) {
			$end_date = $_GET['end'];
		} else {
			$end_date = $_GET['start'];
		}

		if ( isset( WC()->session ) ) {
			WC()->session->set( 'start_date', $start_date );
			WC()->session->set( 'end_date', $end_date );
		}
	}
}
add_action( 'woocommerce_before_single_product', 'bkap_set_bookings_via_get' );