Fix SQLite CRUD PHP

I am teaching myself PHP. From some online tutorials, I created a basic CRUD web page to interact with a MySQL database, using PDO. It all works perfectly! Then I transferred the DB contents into a sqlite database, adjusting the code in the standard ways so that it should work with sqlite. But it gets errors!
So I did something wrong in the adjustments. Your job is to find and fix this, so the sqlite version works like my regular MySQL version. Put ‘Blue Sea’ in your response bid so I know you read this.