I know that this class isn't really the ultimate or the very best out there, but I would be lying if I say that I feel that this class isn't a good one. I never really met a database access wrapper class that does everything I want it to (phpBB3 is a possible exception), but taking a class from another system and hooking it up to work with mine... felt like I was stealing.
So I wrote my own and called it the Ultimate solution. What I feel would make it ultimate though is addition to PDO and MySQL(i) as well as regular MySQL. I know MySQL and so I wrote the class for MySQL but now that I'm getting too comfortable with MySQL I think I'll learn MySQL(i) and a PDO and rework this entire class into classes.
My OOP skills are improving and I'm learning the advantages of interfaces, abstract classes, implementation and extensions and I think I will include some of these class things (declarations?) in with this class in an attempt to make it more secure... I mean with interfaces, if there are everything in the database class what was inaccessible to outside classes... doesn't that make it stronger? Obviously I still need to do some more research and if you find something feel free to email me or something.
I know that sometimes regular security isn't enough, or maybe I'm just paranoid... current security features are:
1) Filtering of SQL query functions passed through the class (SELECT, JOIN, TRIM, etc)
2) Filtering of SQL functions passed through the class (CREATE, DROP, ALTER, INSERT, etc).
3) private functions, variables... protected SQL credentials
4) Error Handling
5) Automatically cleans user input (from form submittions)
I really am striving for this class to be the ultimate package/solution and I am improving my database skills and OOP skills.