foreach ( $results as $result ) {
    $reception_list = explode( ',', $result['reception_list'] );
    $party          = explode( ',', $result['party'] );

    if ( 'yes' === strtolower( $result['invited_to_reception'] ) &&
        empty( $result['reception_list'] )
    ) {
        $party_guests = $party;
    } else {
        $party_guests = array_intersect( $reception_list, $party );
    }

    printf(
        '<p>Reference: <b>%s</b><br />',
        esc_attr( $result['reference'] )
    );

    foreach ( $party_guests as $guest ) {
        $guest_name = trim( $guest );
        printf(
            '<label><input type="checkbox" value="%s" /> %s</label> ',
            esc_attr( $guest_name ),
            esc_html( $guest_name )
        );
    }

    echo '</p>';
}