I am learning the Model relationship types in cakephp.  

I have built two tables and in one of the Table A,   

I got these fields in it:  

```
Table A {postID, topic, content} 
Table B {replyID, content, postID}

```

And when I ran the web page, a bunch of error related to SQL  
 popped up saying that
cakephp couldn't find post\_id.  

It is weird that I have already declared   

the $primaryKey to be using postID in the tableA.php under Models folder,   

but cakephp seemed want me to change the ID field to post\_id instead of postID,
because the error disappeared after I have changed the primaryKey to post\_id.

ANy ideas?