Creating sound - reading out alphabets - in PHP

Question

I've been doing a captcha script lately and was rather successful with it. However I want to create another script that creates a sound which can be used with the captcha.

E.g. the captcha script generates A2B1FD - and the sound script must be able to read out A, 2, B, 1, F, D. How do I go about doing this?

I know it's something to do with OpenAL but how to I start?

Cheers Sam Yong

EDIT: I also wish to know how can I load the sound file loaded from the script in the browser and play it so that the end-user can hear.

Edit 2: I am also looking at the possibility of Text-to-Speech (platform independant) in PHP

Answer 1

Probably the easiest way would be to record 36 individual audio files of each letter and number, and then have your PHP script concatenate these on-the-fly to deliver a single audio file to the browser.

Here's an example script that uses PHP to concatenate WAV files. In fact, it's for the same purpose - creating a captcha.

Once you've created the unique file for that code, you would just embed it in the browser using standard HTML object and embed techniques.

A tidier method would be to use Flash to do this, but be aware that Flash can hog system resources for the site user - and that can cause problems for visitors using a screen reader as their software can't get enough CPU time to work effectively. Thus you could possibly be defeating the very users you're trying to help.