PHP's instanceof operator.

instanceof.txt

$ php -r 'var_dump('test' instanceof \Exception);'
bool(false)
$ php -r 'var_dump(null instanceof \Exception);'

Fatal error: instanceof expects an object instance, constant given in Command line code on line 1
$ php -r 'var_dump(1234 instanceof \Exception);'

Fatal error: instanceof expects an object instance, constant given in Command line code on line 1
$ php -r 'var_dump(array() instanceof \Exception);'
bool(false)