klog

Overview: Learning PHP Data Objects, by Dennis Popel, is an introduction to PDO, which walks through the building of a believable test example - a library manager for your home library. Each chapter introduces a new facet of PDO and shows how to rewrite the appropriate parts of the application to slot the new ideas in. Very clear and easy to read. Non-PDO subjects are appropriately kept to the appendices.

I really couldn’t find very much about this book that I didn’t like. Ignoring the appendices, the book is 154 pages purely devoted to teaching PDO through examples, including error handling, working with BLOBs, even the creation of the M in MVC (Models).

I mentioned MVC there. One of my gripes with most tutorials of MVC is that they introduce the concept simply, then provide pages and pages of code with the end product which is “hello world”. Why I should go to all that trouble instead of simply writing <php echo 'hello world'; ?> to the screen usually escapes me. Dennis, however, concentrates solely on the Model and shows exactly why it’s a great idea. I think some more separation of concerns would have been better (don’t mix Author and Book SQL in the same object, for example), but the ideas were all good.

I think that if Dennis was going to show how the Model works, he should also have gone a little further and showed an example of an Active Record pattern as well. But I guess the point of showing MVC was more to show /an/ example of abstraction of the DB code, and that was sufficient.

The book covers a Library manager application all the way through from conception to implementation, demonstrating at all points that the code works with SQLite and MySQL (and by implication, all other DBMS’s) with a change of only the connection string.

Possible problems are explained clearly and solutions are provided. For example, Dennis explains why, after you compile the query select * from books, PDO (and indeed the database itself) does not know how many rows it will return. A solution, in the form of a very smart getRowCount() function shows a query-agnostic method for counting results of an arbitrary line of SQL.

Other areas that are covered in the book include error-handling, prepared statements and transaction-handling.

PDO can handle Prepared Statements even if the underlying DBMS cannot handle it, so it is possible to write your code in a cross-platform way. Examples of why you should use this are provided. One of the examples shows an efficient way to handle insertion or updating of a table using the same parameters for both cases, with the row-handling function deciding whether to use update or insert based on whether an ID was provided.

I feel the Transactions section could have been expanded a bit further. It is not explained how PDO handles this for DBMS’s that don’t internally support transactions, and I wouldn’t like to assume that they work all the time, only to find after deleting critical data that it’s not supported.

Overall, I enjoyed reading this book. Dennis is a good writer and I think he explained his thoughts very clearly.

On an aside, my four-year-old son Jareth loves Packt Publishing’s books. Sometimes when I go to read another chapter, I need to covertly steal the book I’m reading back from him. For a while, he made it a bed-time ritual to grab all the Packt books he could find around and bring them up with him to read in bed. I think he loved the screen-shots and the frequent code samples. He’s high-functioning autistic and likes literary constructs, and programming books are perfect for him in that regard. Thanks Packt, you’ve made my son (and therefore me) happy.

I’ve been doing well over the last two weeks - I started with an ANN which can balance a pole, and upped that by then creating a net which could recognise letters.

The plan for today is a bit more ambitious. I’m writing it down here in case it takes longer than a day to write it. In general, I want to write a PHP application which will allow you to upload images, which the ANN will then try to recognise. If it gets it right, all well and good. If it gets it wrong, you can correct it.

Some milestones for the project:

• readers can upload images and have them tested and/or added to the training sequence
• extraction of image pixels using <canvas>
• automatic creation of new neurons as they are required
• best net is stored on server, so new readers always start with a working net

I think this may grow into a damned cool thing - I’m already thinking of other cool features like distributed nets, or background nets which can be placed in other pages of a site so the thing can continue training even though the user is not actively viewing the thing (that might be a bit cheeky though).

Anyway - now that I’ve written what I intend to do, I suppose I’d better actually do it.

It’s not even been a month yet, but I think 1.1 is ready. 1.0 was the real test, and a load of bug fixes went into it on an almost daily rate until a week ago, when no more bugs were reported. I managed to squeeze in a number of the requested improvements, and KFM 1.1 is now ready for release.

I think the most important part of this current release is that SQLite PDO is now supported. This means that a person who does not have a MySQL or PostGres database as part of their hosting package might still be able to use KFM. This involved building a database abstraction layer abstraction layer (not a typo), so MDB2 can be used for the “normal” databases.

It was fun to solve the IE7 problem where normal JavaScript dialogs are considered to be “popups”. The way I solved it was to create a modal window which passes its value forward to a referred function. Those of you that are good JavaScript writers might be interested to read the source and see my solution - I’m damned proud of it!

There’s a lot of work to do to prepare KFM for the next big thing (changeable view types - icon view, details view, etc), and I’m “rearing at the bit” to get started on that!

Anyway, please download and try it!, and if you feel very happy that I’ve improved your customers’ online experiences, there is a handy PayPal button just below the big green Download button.