Padraic Brady has posted about an issue he noticed when working with regular expressions and the "word" character type to find something that's alpha-numeric (including an underscore):

You can find the "word" generic character type used in a lot of PHP code including the Zend Framework. The problem is that the assumption above is incorrect. Now, most of the time these act identically because PHP is compiled using its own packaged PCRE library. However, I've seen more than once systems where this is not the case. Usually in some non-English capacity where additional locale support was considered necessary or standard practice.

The problem comes when PHP is compiled against a custom PCRE library, making it more locale-aware. He gives instructions on how to get this to a testable state on your environment (using an updated PREC library) and get it working for characters in French, like the accented "a" or "e".

Jordi Boggiano had the "pleasure" of discovering a small quirk with PHP's glob function in an application he was working on - watch out for directories that contain square braces, they won't return in the results!

Working on some personal project that lists a bunch of stuff on my hard drive, I found out that directories that contain square brackets (those []) don't return any results for the simple reason that glob reads [stuff] as a character class, just like in regular expressions. When you know it it makes perfect sense, but when you don't, the documentation is really not so helpful. Of course it mentions libc's glob() and unix shells, but not everyone knows what that implies at first glance.

He tried a few things to get around the bug (including escaping the brackets in the directories) but ended up writing a function (glob_quote) to handle the escaping of all of the meta-characters glob might need to escape to return all of the files and folders correctly.

On the PHPFreaks.com blog today there's a quick new post looking at one of the special backslash strings that doesn't get talked about very much - K - but is quite powerful.

One backslash sequence that doesn't get much attention is K. What this handy little assertion does is match the position of whatever string comes before it in the pattern, then it in essence resets the match. At that point it starts a new match with whatever comes after K from the current location in the subject string.

They include a series of PHP code examples showing how use can use it to work around some of the issues with lookbehind assertions. They also include a few benefits and drawbacks of using them over lookbehinds.

New on DevShed today there's the fifth part of their series looking at validation and filtering in PHP5 applications.

Among the enhancements that were introduced originally in PHP 5, there's one powerful extension that has been all but ignored by many programmers until now, quite possibly because they weren't aware of its existence. [...] In this fifth part of the series, I'm going to discuss the usage of the [filter] extension for checking if the value that has been assigned to a given variable follows a specified regular expression pattern.

They include examples of using the FILTER_VALIDATE_REGEX option for filter_var to check the input against a given format. You'll have to find an introduction to regular expressions someplace else, though - they just assume you know how to work with them.

PHPBuilder.com finishes off their "ABCs of PHP" series today with this last tutorial covering a script to fetch the latest headlines from Slashdot and parse the resulting XML with regular expressions.

Well my loyal readers (and you must be loyal if you've made it this far). Here we are at the final installment of the 'ABC's of PHP' where we are going to put some of what we've learned over the past couple of months into practice. We're going to go step by step through a small script to read the latest headlines from Slashdot.org [...] As the feed is very simple however, I decided to simply just use 'preg_xxx' calls to elaborate on the material from part 9 on using reg-ex calls, if you where reading anything more complex then you would almost certainly want to use the proper XML functions.

The actual parsing is pretty simple - grabbing each story, date, time and title element from the XML content and pushing it all into an array. The result is a nice array you can loop through and display via the method of your choosing.

On his blog today Sameer Borate has posted a quick tutorial on how to use a PEAR package to do search and replace on your files from inside of PHP.

Searching and replacing content in files is a common task all of us do regularly. [...] Search/replace is easier from a shell prompt or an editor, but what if you have to do the same programatically in php. File_SearchReplace is a pear package that helps you search/replace in files through a nice object oriented interface.

Installation is simple (via the "pear" command line tool) and using it is just as easy. He gives a few examples of how it can be used - everything from a simple find and replace out to a more complicated regular expression search to be replaced with a string.

Kevin Waterson has posted an extensive tutorial to his site today giving a great look at regular expressions in PHP (and just regular expressions in general).

At its most basic level, a regex can be considered a method of pattern matching or matching patterns within a string. In PHP the most oft used is PCRE or "Perl Compatible Regular Expressions". Here we will try to decypher the meaningless hieroglyphics and set you on your way to a powerful tool for use in your applications. Do not try to understand all this in a single sitting. Instead, take in a little and come back as you grasp various concepts.

He starts with simple string matching, showing how to get values from the middle, end and beginning of it then moves on to the next more powerful step - using meta characters. He outlines these as well as sequences and modifiers. There's plenty of examples here so there's almost no chance of getting lost.

It's a great tutorial that I'd recommend to anyone who things regular expressions are "just too hard" or it looking to figure out their power.

On the Debuggable blog, Felix Geisendorfer shows how to create a string parser that allows you to pull out parts of the string you don't currently want manipulated to be put back later.

If you've ever written any non-trivial String processing code, you've probably ran into the situation where you wanted to exclude certain parts of your string for a certain operation. Usually that would mean you have to tokenize your string, or adjust the operation you want to run so it doesn't affect the part of the string you want to exclude from it. Both of those solutions can be fairly time intensive so I was looking for a shortcut and found one.

He provides the code for this string substitution class, a method substitute() that matches based on a regular expression and, if found, stores the parts for later use.

Michael has posted a simple script today that takes in XML data and spits back out an array on the other side:

The function takes the specified XML data (which must be in valid XML format) and converts into an array. Any attributes in the XML elements are dropped an only the element values are placed in the array.

The code uses a combination of XPath, DOM, and regular expressions to parse the given XML content.

Mike Naberezny has posted a few more articles to the "Rails for PHP Developers" website (based on this book) covering some more of the basics.

There's three new tutorials posted:

• Ruby Block Scope - the basics of Ruby block scope, a common point of confusion for PHP developers new to Ruby.
• Variable Arguments - an article that shows two common API patterns found in Rails, variable arguments and option hashes, and how to implement them both in PHP.
• Regular Expressions in Ruby - a useful reference that maps all of the common PHP regular expression functions to the equivalents in Ruby.

Check out the rest of the site for even more great content.