Good work, but there is quite a bit that needs to be fixed. Here is what I want done (all small things):

• Are so many comments really required (especially towards the beginning)? You heavily comment the declarations (which honestly is not necessary) yet leave out comments on the actual processing code.
• Don't trigger errors when the script can still continue. Some procedure had changed and we are no longer going by exceptions, just return something to indicate failure.
• Those constants are really not necessary.
• Why are you assigning $this->query then using it once? Wouldn't it make more sense just to directly run the query?
• Use parameters for the creation, dont make the programmer assign two class variables than run it.
• This is a general database programming rule, always always always go by unique ID when possible. Make delete() delete by an ID given in a parameter.

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