When to use " is same as" and when to use "=="
Looking at the Twig code, they have this documented for the “same as” test:


  Checks if a variable is the same as another one (=== in PHP).


I won’t re-hash the details of === vs. == in PHP because there is an excellent comparison here: https://stackoverflow.com/questions/80646/how-do-the-php-equality-double-equals-and-identity-triple-equals-comp

The money quote is:


  == compares the values of variables for equality, type casting as necessary. === checks if the two variables are of the same type AND have the same value.


And here’s what the PHP docs have to say:

http://www.php.net/manual/en/language.operators.comparison.php