[Zayne_mybb_import19817]

Well since you asked me to correct you I guess I can.
Your query is wrong.

Code:

SELECT * FROM posts WHERE user = '' and 1=1--'

When in fact it would be (As you already stated in the thread)

Code:

SELECT * FROM posts WHERE user = '$enteredvalue'

Not quite sure why you moved the payload outside the point of injection.

Yeah what she said ^, and try to avoid using deprecated functions.

I will update this when I get home. I used deprecated php functions to show examples of poor php coding that leaves you open to sql injection.

Yeah I figured. What I meant but didn't state was that developers (or anyone for that matter) shouldn't be using old deprecated functions. In-fact they was released a long time ago (can it be 12-15 years?) which means the API is probably pretty out-dated (or just bad) and that is the main reason they decided to put out a new library of functions with a better API. Secondly, I am sure these deprecated functions will be removed in the near future. When the functions are removed, your vulnerable piece of code will not run correctly. 
What I tried to say is that you could of still demonstrated this with another set of functions which is not deprecated. For example not escaping the concentrating input correctly.