Undefined variable: _ (underscore)

RouterOS Scripting
1

Hi,
I’m using PHP Api class (http://wiki.mikrotik.com/wiki/API_PHP_class) and i’m still getting “Undefined variable: _” in function read().
The error occures randomly.
I tried get new version of PHP Api class (1.4). I made there one little modification:
Modified this:

if ($_ == "!done")
       $receiveddone = true;

to this:

if ($_ == "!done"){
       $receiveddone = true;
}else{
	$receiveddone = false;
}

Because “Undefined variable: receiveddone” was thrown.

I’m getting pretty desperate with the “Undefined variable: _” error. Any googling wasn’t helpful.
Thanks in advance.
Rax