PHP variable / function / class names using special characters

Question

I understand that the underscore _ is an acceptable character for naming variables / functions / classes etc. However I was wondering if there are any other special

Answer 1

A valid {variable | function} name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.

http://www.php.net/manual/en/functions.user-defined.php http://www.php.net/manual/en/language.variables.basics.php