Increment behavior on strings – PHP easter egg?

PHP follows Perl’s convention when dealing with arithmetic operations
on character variables and not C’s. For example, in PHP and Perl $a =
‘Z’; $a++; turns $a into ‘AA’, while in C a = ‘Z’; a++; turns a into
‘[‘ (ASCII value of ‘Z’ is 90, ASCII value of ‘[‘ is 91). Note that
character variables can be incremented but not decremented and even so
only plain ASCII characters (a-z and A-Z) are supported.
Incrementing/decrementing other character variables has no effect, the
original string is unchanged.