iamcal.com Since May 2000

Test your regular expression skills via some interactive regex crosswords. I'd suggest signing into Facebook before you start (if that's your sort of thing), since it will lose any progress when you do. It took me a little under an hour to complete them.

There are two answers guaranteed to show up on nearly every PHP question on Stack Overflow - use the mysqli/PDO extension instead of the deprecated mysql one (to avoid SQL injection), and that you can't parse HTML with regular expressions.

With that in mind, my favorite two answers:

• [How PDO is still vulnerable to SQL injection attacks](http://stackoverflow.com/questions/134099/are-pdo-prepared-statements-sufficient-to-prevent-sql-injection/12202218#12202218) by Anthony Ferrara
• [Parsing HTML with regular expressions](http://stackoverflow.com/questions/4231382/regular-expression-pattern-not-matching-anywhere-in-string/4234491#4234491) by Tom Christiansen

i've been going back and forth with dominic sayers for the last couple of weeks on RFC-based email validation. we both have php functions (mine, his) that pass a huge (and esoteric) test suite. who says RFCs are dull? (hint: they are)