如何用sql数据填充html下拉列表?

I am new to PHP, hoping for some help please. I am trying to populate an HTML dropdown list with data from my SQL database. I would like to be able to select an item from a dropdown list that would then fill an HTML table with the associated record from the database. So far I have managed to connect to my database and retrieve all of the data from the relevant table. I am new to PHP, hoping for some help please. I