custom hook

/**
 * View Content Hook Adjustment
 * Limit points to be awarded once per day per unique post.
 * @version 1.0.3
 */
add_filter( 'mycred_add', 'mycred_pro_view_once_per_post', 10, 3 );
function mycred_pro_view_once_per_post( $reply, $request, $mycred ) {

        if ( ! in_array( $request['ref'], array( 'view_content', 'completing_quiz_full' ) ) || $reply === false ) return $reply;

        if ( $request['ref'] == 'view_content' ) {

                $post_id             = absint( $request['ref_id'] );
                $post_categories     = wp_get_post_categories( $post_id );

                if ( in_array( 89, (array) $post_categories ) || in_array( 90, (array) $post_categories ) )
                        return false;

        }

        global $wpdb;

        $until = current_time( 'timestamp' );
        $check = $wpdb->get_row( $wpdb->prepare( "
                SELECT *
                FROM {$mycred->log_table}
                WHERE ref   IN ( 'view_content', 'completing_quiz_full' )
                AND user_id = %d
                AND ref_id  = %d
                AND ctype   = %s
                AND time BETWEEN %d AND %d;", $request['user_id'], $request['ref_id'], $request['ctype'], mktime( 0, 0, 0, date( 'n', $until ), date( 'j', $until ), date( 'Y', $until ) ), $until ) );

        if ( isset( $check->ref_id ) )
                return false;

        return $reply;

}