Are there any good comprehensive PHP programming books or articles/tutorials out there that I can learn about how to integrate SMS communications with my PHP application?
I've done a Google search and found some information scattered about the web but I need a comprehensive resource. I want to learn everything I can about how a PHP application communicates with SMS and vise versa. If someone can point me in the right direction that would be great.
No specific knowledge is required to be able to programmatically interact with the services of an SMS provider unless, of course, you're planning to become an SMS provider.
Commercial SMS providers supply an SMS to HTTP bridge, some form of interface between SMS services and an HTTP server. You don't need to know how this SMS to HTTP bridge works.
Data sent via SMS to your number will be caught by the SMS provider and POSTed to a URL of your choice for you to then collect and handle as required.
Data you wish to send via SMS will be POSTed to a URL specified by the provider.
So in integrating with an SMS service, either in PHP or any other language, you only need to be familiar with handling incoming POST data and with making outgoing POST requests.
I once evaluated a set of UK-based SMS providers for a UK-based dating site, with the view of integrating SMS features in to a PHP-driven service. My answer is based on my experience in doing this.