callerid variable holds the value of the Caller ID.
Caller ID, also known as ANI in the telecom industry, is the phone number of the telephone that initiated the call.
lastinput variable holds the value of the last user input. The lifetime of this operation is guaranteed only till the next API is invoked. This is most useful to get the user input when native PHP APIs (e.g. echo, print) have been invoked and the user has interrupted the voice rendering with DTMF or speech.
streamlen variable holds the total length of the of the last playback operation. The value is specified in milliseconds. Any function that can render voice output will update this value (e.g. prompt, speak, play, echo etc)
streamposition variable holds the value of the position till where the last playback operation was completed. The value is specified in milliseconds. Any function that can render voice output will update this value (e.g. prompt, speak, play, echo etc)