The specified permitted characters in variable names (including the first character) are somewhat more permissive than you might expect.
The specified regex is [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]* (from ./functions.user-defined.php)
On running the following you can see those outside of [a-zA-Z0-9_] that work. Your browser/shell may not display all properly, and some editors (I tested in Textmate) may simply remove things it doesn't grok as whitespace. However, there are some pretty sexy characters in there should you be looking for a unique namespace which is not too lengthy. Using them can be inconvenient for others who may not have a suitable keyboard for single-stroke entry (mine is Spanish). Best used for a program's internally relevant methods - which are those we wish least to pollute a namespace.
<?php
header('Content-type:text/plain; charset=utf-8');
function unichr($u) {
return mb_convert_encoding('&#'.intval($u).';', 'UTF-8', 'HTML-ENTITIES');
}
for($i = hexdec("7f"); $i <= hexdec("ff"); $i++) echo unichr($i)."\n";
function ñ(){
echo "I'm ok!";
}
ñ();
?>