CRUD使用prepare语句不起作用。

Database connecting is working. The SELECT AND UPDATE FUNCTION in the class is not working at all.It is not even showing errors to help me sort out the problem. I am trying to learn how to use the prepare ,bind-param and execute statement. Please can someone help look at the codes and advise what may be wrong with it. Just spent loads of hours on this and just cant figure where the problems is. please can some help me.I am a novice and writing my very first codes . Many thanks in advance Database connecting is working. The SELECT AND