The following piece of code will help list all objects, arrays and vars in the $GLOBALS variable scope.
< ?php
foreach($GLOBALS as $glob_key => $glob_val){
echo $glob_key." - ";
echo (is_array($glob_val)||is_object($glob_val))?print_r($glob_val,1):$glob_val;
echo "\r\n
";
}
?>
This can be very useful as there is usually a lot of information stored in $GLOBALS by both WordPress and Plugins.