preg_match_all("!(?:0x[a-fA-F0-9]+)|([a-zA-Z][a-zA-Z0-9_]+)!",$equation, $match);
$allowed_funcs = array('int','abs','ceil','cos','exp','floor','log','log10',
'max','min','pi','pow','rand','round','sin','sqrt','srand','tan');
preg_match_all("!(?:0x[a-fA-F0-9]+)|([a-zA-Z][a-zA-Z0-9_]+)!",$equation, $match);
$allowed_funcs = array('int','abs','ceil','cos','exp','floor','log','log10',
'max','min','pi','pow','rand','round','sin','sqrt','srand','tan');