Hangup handlers are subroutines attached to a channel that will execute when that channel hangs up. Unlike the traditional h extension, hangup handlers follow the channel. Thus hangup handlers are always run when a channel is hung up, regardless of where in the dialplan a channel is executing.
Multiple hangup handlers can be attached to a single channel. If multiple hangup handlers are attached to a channel, the hangup handlers will be executed in the order of most recently added first.
Dialplan Applications and Functions
All manipulation of a channel's hangup handlers are done using the CHANNEL function. All values manipulated for hangup handlers are write-only.
Used to push a hangup handler onto a channel.
Used to pop a hangup handler off a channel. Optionally, a replacement hangup handler can be added to the channel.
Remove all hangup handlers on the channel. Optionally, a new hangup handler can be pushed onto the channel.
Adding hangup handlers to a channel
In this example, three hangup handlers are added to a channel: hdlr3, hdlr2, and hdlr1. When the channel is hung up, they will be executed in the order of most recently added first - so hdlr1 will execute first, followed by hdlr2, then hdlr3.
Removing and replacing hangup handlers
In this example, three hangup handlers are added to a channel: hdlr3, hdlr2, and hdlr1. Using the CHANNEL function's hangup_handler_pop value, hdlr1 is removed from the stack of hangup handlers. Then, using the hangup_handler_pop value again, hdlr2 is replaced with hdlr4. When the channel is hung up, hdlr4 will be executed, followed by hdlr3.