In this new post from the splitbrain.org website (creators of the Dokuwiki application), there's an example of how to join wav files together with PHP with a quick and easy script.

I'm currently working on a CAPTCHA plugin for DokuWiki and thought about providing audio output for users not able to see the image. This is pretty simple for CAPTCHAs - there is no need for complicated speech synthesis because you only need recordings of the 26 possible letters. But you need a way of joining those recordings on the fly...

There was an example he found previously, but it seemed like overkill, so he rolled together his own solution - a 24 line script that takes in the filenames of the wav files and spits back out the joined resource. This functionality has already been added to the CAPTCHA plugin if you'd like to check it out.

Via this digg.com post today, there's information about a new PECL extension that's been committed allowing developers to create wave forms for strings of text.

Yahoo developer Jeremy Johnstone just added a new extension to the PECL PHP library that will allow you to send a string of text and have the extensions spit back out a wave form. This is huge news for those running public sites with the "please enter the text you see here" dialogs. Now you can offer a new alternative to image captcha.

According to its PECL page, it wraps around the Flite voice synthesis library, and can take in text and quickly generate both RIFF and raw wav formats. For more info, check out his new blog entry.