Regular Expressions are a powerful way to parse and evaluate strings. They can be fun sometimes, but there is rarely an indication of the reason why they fail.
I knew it would be satisfying, once I seen this (the Filter extension) in passing on the php.net site. It uses the procedural method, which I think fits perfectly. If you try to throw objects at a novice than most aren't likely to use what you give. It is really simple to use, so there is no longer any excuse for an developer to not be using it, if using PHP 5.2+.
He gives examples of email validation methods both with and without the Filter extension, making it abundantly clear which is easier - a simple call to filter_data validates with no muss or fuss.