As someone who frequents the PHP tag on StackOverflow I pretty often see questions about how to parse some particular aspect of HTML using regular expressions. A common reply to such a question is: "You cannot parse HTML with regular expressions, because HTML isn't regular. Use an XML parser instead." This statement - in the context of the question - is somewhere between very misleading and outright wrong. What I'll try to demonstrate in this article is how powerful modern regular expressions really are.

He starts with the basics, defining the "regular" part of "regular expression" (hint: it has to do with predictability) and the grammar of the expressions. He talks about the Chomsky hierarchy and how it relates to the "regular" as well as a more complex mapping of expression to language rules. He talks about matching context-free and context-sensitive languages and unrestricted grammars as well.

No matter how advanced the techniques that we use, there is always something that we could be doing better. [...] Which one is right? The real problem is that the answer to that question is, "yes." That's because it lacks a specific context in which it can be inserted.

He suggests that, in our quest to figure out what the perfect case for any situation, we stop focusing on the practicality of writing applications to accomplish goals. Sometimes it's not about getting the right theory behind the code - sometimes it's just doing it.

The posts will be researched and go through multiple drafts for professionalism before posting. In this hope, it will strive to enable discussion that isn't flaming and collective of the topic at hand. For as much as I can achieve at my level of writing skill and researching the topic at hand.

He he goes through the purpose of the posts, the areas he's going to focus on, some about the theory that will be used, and the implementation and documentation he'll provide through the series.

Anyways I just posted the following email to internals in a list attempt to get some of the people with php-dev karma to lift their finger.

In the message, he notes the change he's looking for and a suggestion to get it included before RC6 of the series gets released (which has been released as of this post already).

He does go over a bit of the theory and why they are so invaluable, but it's a short section before he gets to the heart of the article - working with regular expressions for:

• positive matching
• matching all instances in a given string
• finding an exact match
• matching the start of a string
• validation of the contents of a string
• checking the length of a string

At the request of a listener to past podcasts, Scott created this one to share some of his experiences and findings along the path of his develoopment. Some of the items covered in the podcast include:

• package and library management
• naming conventions
• the seperation of UI and business logic
• code distribution
• using test harnesses

You can download the MP3 of the podcast directly from here.

I know very little of compiler and interpreter theory and have never (yet) created a working implementation of a compiler or interpreter. What you're about to read or (most likely) skip over is a Head-in-Ass post and feel free to flame me on parts where I'm wrong, which will be most places. Do realize that this is one end user's opinion of the matter and any perceived insult upon any author(s) is not intended and please do not take it as such.

Jacob talks about run-time classes, class optimization, what he "really wants" out of a compiler, namespace functionality, a "phpc" extension, and his opinions on the Zend Engine, other web technologies, and the future of PHP.