--- /dev/null
+# http\Message\Body http\Message\Body::toCallback(callable $callback[, int $offset = 0[, int $maxlen = 0]])
+
+Stream the message body through a callback.
+
+## Params:
+
+* callable $callback
+ The callback of the form function(http\MessageBody $from, string $data).
+* Optional int $offset = 0
+ Start to stream from this offset.
+* Optional int $maxlen = 0
+ Stream at most $maxlen bytes, or all if $maxlen is less than 1.
+
+## Returns:
+
+* http\Message\Body, self.