In order to convert base 26 (hexavigesimal) of just alphanumeric characters (A-Z), wthout integers, (as descibed at http://en.wikipedia.org/wiki/Hexavigesimal), I found this to be useful:
function base_convert_alpha( $str, $from, $to )
{
$r = range( 'A', 'Z' );
$clean = str_replace( $r, array_keys($r), $str );
return base_convert( $clean, $from, $to );
}
echo base_convert_alpha( "BAC", 26, 10 );
//$clean = 102 which then returns 678