A review of "Learning PHP Data Objects"

Packt Publishing recently sent me a couple of books to review. This post is about the second one I received, Learning PHP Data Objects by Dennis Popel. I was excited to receive this book as PDO underlies a lot of the Zend_Db_Adapter objects that I use in my day to day programming. It seemed like a good idea that I should know more about it.

Overview of the book

This book starts out introducing PDO and then takes us on a tour through all its features including error handling and prepared statements along with more advanced features like scrollable cursors.

The first chapter introduces PDO and shows the basics of how to use it to connect to a database, issue a query and retrieve the resultant data. The author also makes the distinction about how the code he is showing is example code and provides pointers to what’s missing (such as proper error messages) if you were to use the code in production. I liked this very much as it’s important as authors that we realise that inexperienced readers have a tendency to copy/paste examples and use as-is. The introductory chapter closes with a look at prepared statements and so covers all the high points of PDO.

Having introduced the subject, chapter 2 looks in detail at using PDO to connect to a database. This chapter is more tutorial-ish and the code is presented to be typed in. A worked example of a book database is used from here on throughout the rest of the book. The author appears to expect the user to learn what the code does by reading the comments within the code body, as there is little explanation of what the code does in the prose. One thing that’s tricky is that when there is explanation after a code block, it’s hard to work out which bit of the block the author is referring to. On the whole though, the tutorial nature provides step-by-step progress for people who learn best that way.

Chapter 3 covers error handling. I was pleased to see this important topic given an entire chapter and so early in the book. Error handling is not an after thought here. This chapter provides a good discussion of the types of errors that you will encounter and then provides instructions on how to handle them. Again, the tutorial aspect of the book is emphasised with lots of code to type in. Some of it is in bold, but I’m not sure why as no reference is made to it in the prose. This chapter also starts a dangerous trend where four pages of code is presented (without line numbers) and then the following page or so dissects the code with reference to line numbers that do not exist! This makes the explanation of the code really hard to follow, especially when the you get to the section about lines 189 to 191… This chapter also continues the tutorial by building more pages and showing you how to check for errors along the way.

Chapter 4 studies prepared statements and shows how to use them. Positional and named placeholders are looked at, along with how to insert blobs using bound parameters. In this chapter, the bold sections in the code make more sense as they are referenced in the prose. Again, we have pages of code with no line numbers and then are asked to study lines 60 to 73. The information in this chapter is nevertheless very good and I learnt stuff :)

Having looked at getting data into the application, chapter 5 looks at retrieval and rowsets. This chapter covers counting the number of rows returned and limiting rowsets. It’s much shorter as it covers less topics and I’m glad the author didn’t pad the chapter just to get the page count up! Chapter 6 is also relatively short, but this time covers a lot of ground. These are advanced topics and include connection attributes, buffered queries, dsn files for connections and transactions. The transactions section gets the most space and is covered quite less, though with rather less prose for the volume of code than I would have liked.

The last chapter in the book is a bit of an odd ball as it looks as designing a model within an MVC application. To me this didn’t fit with the specialist PDO nature of the book, and I’d have rather have had more space devoted to transactions or database specific issues.

In summary

This book is an good, detailed tutorial for understanding PDO. It is not a reference book and so relatively hard to dip into to look up a specific thing. If you learn by starting from scratch and working your way through, then this is a very good book. The biggest distraction for me was the long code listings. It would have been better to have either put in line numbers or interspersed the code with the textual explanations.