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add_filter( 'easy_booking_one_date_price', 'wceb_early_bird_pricing', 40, 5 );
add_filter( 'easy_booking_two_dates_price', 'wceb_early_bird_pricing', 40, 5 );

function wceb_early_bird_pricing( $new_price, $product, $_product, $booking_data, $price_type ) {

    // Get current date
    $current_date = strtotime( date( 'Y-m-d' ) );

    // Get start data
    $start_date = strtotime( $booking_data['start'] );

    // Get interval between current date and start date
    $interval = absint( ( $start_date - $current_date ) / 86400 );

    if ( $interval >= 11 ) {
        $new_price *= 0.95;
    }

    return $new_price;
}

// Maybe display price detail
add_filter( 'easy_booking_booking_price_details', 'wceb_display_early_bird_discount', 10, 3 );

function wceb_display_early_bird_discount( $details, $product, $booking_data ) {

    // Get current date
    $current_date = strtotime( date( 'Y-m-d' ) );

    // Get start data
    $start_date = strtotime( $booking_data['start'] );

    // Get interval between current date and start date
    $interval = absint( ( $start_date - $current_date ) / 86400 );

    if ( $interval >= 11 ) {
        $details .= '<br />' . __( 'Price include a 5% discount', 'easy_booking' );
    }

    return $details;
}