prefix_get_bookings_ending.php

<?php
/**
 * Get all bookings with an end date in a specified number of days time
 */
function prefix_get_bookings_ending() {

	// How many days in advance should we send the email?
	$days = 3;
	$date = date( 'Y-m-d', strtotime( '+' . absint( $days ) . 'days' ) );
	error_log( $date );

	$args = array(
		'post_type'			=> 'bfwc_booking',
		'posts_per_page'	=> -1,
		'meta_query' 		=> array(
		'relation'			=> 'AND',
		array(
			'key'     => 'bfwc_end_date',
			'value'   => $date,
			'compare' => '='
		),
		array(
			'key'     => 'bfwc_status',
			'value'   => 'cancelled',
			'compare' => '!='
			)
		),
		'fields'		=> 'ids'
	);
	$bookings = new WP_Query( $args );

	// A list of bookings
	$booking_ids = $bookings->posts;
	if( $booking_ids ) {
		foreach( $booking_ids as $booking_id ) {
			prefix_send_reminder_email( $booking_id, $date );
		}
	}
	wp_reset_postdata();

}
add_action( 'woocommerce_scheduled_sales', 'prefix_get_bookings_ending' );

/**
 * This function sends the email
 */
function prefix_send_reminder_email( $booking_id, $end_date ) {
	
	$booking_product_id = get_post_meta( $booking_id, 'bfwc_product_id', true );

	$to = get_post_meta( $booking_id, 'bfwc_user_email', true );

	$subject = __( 'Your booking', 'bfwc' );

	ob_start();

	wc_get_template( 'emails/email-header.php', array( 'email_heading' => $subject ) );

	$content = ob_get_clean();
	
	// Format the date
	if( function_exists( 'bfwc_format_date') ) {
		$end_date = bfwc_format_date( $end_date );
	} else {
		$date_format = get_option( 'date_format' ); // no longer in use since 1.4.4
		$end_date = date( $date_format, strtotime( $end_date ) );
	}

	$message = sprintf(
		'<p>%s<p>',
		sprintf(
			__( 'Your booking is coming to an end on %s', 'bfwc' ),
			$end_date
		)
	);

	$message = apply_filters( 'bfwc_reminder_email_content', $message, $booking_id );

	$content .= $message;

	ob_start();

	wc_get_template( 'emails/email-footer.php' );

	$content .= ob_get_clean();

	wc_mail( $to, $subject, $content );

}