Asterisk: The Future of Telephony, 2nd Edition

Appendix E. Asterisk Dialplan Functions

Dialplan functions are very powerful, and once you begin using them, you will wonder how you got along without them. Functions are used in the dialplan in a similar manner to variables. If it helps, you can think of them as intelligent variables (or for those of you from the database world, variables with triggers). When you invoke them, they perform a specific action, and their result becomes a part of the command in which you have included the function (in exactly the same way as a variable would).