无法将参数绑定到WHERE子句PDO

I use a lot of sql statements using PostgreSQL and PHP and many of them have variables in the 'WHERE' clause. I can get prepared statements to execute just fine for INSERT and UPDATE but I can't make it work for SELECT statements with variables in the WHERE clause. I have scoured google for an answer with no success. Please take a look at the example below. This is to select a recent reconciled bank balance from a table called bankrec. What am I missing?I use a lot of sql statements using PostgreSQL