warning if variable does not exist - php

Question

If I try to use a variable which doesnt even exist in PHP, I dont get any errors or notices. In the example below the return value is "null". I'd like to see some form of notification if that happens so that I can find bugs in my code more easily.
echo $doesNotExist -> something; //returns null
The error reporting in my php.ini is the following
error_reporting = E_ALL
What do I have to do to see notifications when accessing varibles that don't exist?
To clarifiy this:
I know that I can check if a variable exists by using isset(). That's not what I want though. I want to get a notification in case I accidentaly try to use a variable that does not exists. For example if I misspell the name of a variable.
display_errors = On is in my php.ini

Answer 1

As well as error_reporting, you may need to turn on display_errors, which should be off in production environments.
Production environments can use log_errors instead, which outputs the errors to the file named in the error_log directive.

Answer 2

I generally use thw following;
if(isset($var) && !empty($var)) {
//Do something with $var
} else {
//Define $var
}
As said in a previous answer you also need to turn error reporting on in the php.ini

Answer 3

what you do is perfectly valid in PHP. It just creates and instantiates that variable at runtime, and doesn't throw an error like other languages.
even isset would not work too well. Say you set an object variable with a wrong name. If you do isset on that name, it will be true. If you do isset on the correct name, it will be false.
Example:
class test{
public $name1;
}
$test = new test;
$test->name2 = 'wrong';
var_dump($test);
prints: object(test)#1 (2) { ["name1"]=> NULL ["name2"]=> string(5) "wrong" }