[SalesForce] trigger send thank you email when a new subscriber is added to the list -exacttarget

Your processing page is a landing page consisting of only ampscript and needs to look something like this:

%%[

VAR @var1, @var2, @var3, @emailaddress, @result

/* Get variables */
SET @emailaddress = RequestParameter("emailaddress") 
SET @var1 = RequestParameter("var1") 

/* etc. */

/*Update/insert the records. See this for explanation of arguments http://help.exacttarget.com/en/documentation/exacttarget/content/ampscript/ampscript_syntax_guide/data_extension_ampscript_functions/#UpsertData   */

SET @result = UpsertData("DE_NAME", 1, "emailaddress", @emailaddress, "var1", @var1.... )

IF @result >= 1 THEN 
  Redirect("http://success.html")
ELSE
  Redirect("http://fail.html")
ENDIF

]%%

I would set up a new Triggered Send definition in the account and then call it manually using either the SOAP or REST API's. Populate the Triggered Send request with the info of the new subscriber you just successfully added. There are a couple ways to do this with ET's APIs.

SOAP http://help.exacttarget.com/en-US/technical_library/web_service_guide/technical_articles/send_triggeredsend_email/

REST https://code.exacttarget.com/api/messaging-messagedefinitionsends-send

Fuel SDK You can also send a triggered email in PHP with the FuelSDK. The Fuel SDK is an abstraction layer on top of the API's listed above. https://code.exacttarget.com/sdks/fuel-sdk-interacting-triggeredsend