The page at http://www.php.net/manual/en/language.functions.php doesn't specify (as far as I can see) what constitutes a legal function name. On the other hand, http://www.php.net/manual/en/language.variables.php does contain a regexp specifying variable names.
Could someone who knows the pattern specify it in the manual? Unfortunately I don't know it myself, or I'd add it in a note. Thanks, Richard
