$message vs. $$message in PHP.
$message is a variable with a fixed name. $$message is a variable whose name is stored in $message.
For example:
$Message means simple variable store data.
$$Message means variable variable.
That is, a variable name which can be set and used dynamically
$Message = 'hello';
print $Message; // print hello
$$Message = 'world';
means $hello ='world';
now if u print $$Message;
menas $hello;// print world;
if u print $Message $($Message); // print hello world;