Charge Post Author for Link Click

add_filter( 'mycred_add', 'mycred_charge_post_author_for_click', 999, 3 );
function mycred_charge_post_author_for_click( $reply, $request, $mycred ) {

    if ( $reply === false || $request['ref'] != 'link_click' || ! is_single() ) return $reply;

    global $post;

    if ( ! isset( $post->post_author ) ) return $reply;

    $author_id = $post->post_author;
    $balance = $mycred->get_users_balance( $author_id, $request['type'] );

    // Charge if author can afford it
    if ( $balance >= $mycred->number( $request['amount'] ) ) {

        // Charge the amount the user who clicked receives from the author
        $mycred->update_users_balance( $author_id, 0-$request['amount'] );

        // Add a log entry
        $mycred->add_to_log(
            'link_click_charge',
            $author_id,
            0-$request['amount'],
            'Charge for link click',
            $request['ref_id'],
            $request['data'],
            $request['type']
        );

    }

    return $reply;

}