cwarn23,

I doubt you'll find a free SMS service. The usual approach is to find a gateway provider or broker that has the kind of service your after.

Well now that you mention gateway provider, I guess you would say that this script I'm after acts as a gateway provider and has no external dependencies. I just need to know how.

Couldn't you send emails using the wireless provider's gateway?
usernumber@wirelessprovider.tld?

Well the thing is that theoretically it should be possible for php to send the SMS without any external dependencies including email and curl. I know that sockets would be involved. But the question is how to make a custum function library the sends+receives SMS's just like how the mail() function sends emails without another company involved. And I know that I should be able to do this intirerly in php as sockets is designed for this sort of stuff.

So in basic I'm looking for a php script that sends and receives SMS messages where php directly communicates with the SMS protocol (not an api) and no external server, no external companies and no email involved.

I haven't heard of such a script and I was searching hard for one a couple of years ago when setting up a school contact subsite. Everything I've seen boils down to gateway providers. I'd be v.v. interested in a script. I think everybody would be. No need for a Blackberry!

For More information:
Wikipedia SMS Gateway

Here is something simple, but still would cost money. This type of service will never be free.

http://invalid.name/wiki/index.php/S...an_SMS_Gateway

OMG I CAN'T BELIEVE THIS!!!
I followed the wikipedia link codejoust posted and found another wikipedia link in that page SMPP Protocol which lead me to the official open source protocol for SMS. It is written in Java but I shall be the first to convert it to php. So it is totally possible to send free SMS and will republish code when finnished as the licence says I'm allowed to redistribute it as long as it has their copywrite notice. This is so exciting.

You really think cellphone companies are going to let you send free messages through their equipment. Not going to happen.

SMS providers buy a bulk of messages from those companies at a discounted rate. Then they resell them, adding some to the price so they can make some money. It won't be possible for you to do this for free.