class CharacterReference

class CharacterReference {
    protected static $numeric_mask = array(
        0x0,
        0x2ffff,
        0,
        0xffff,
    );
    
    /**
     * Given a name (e.g. 'amp'), lookup the UTF-8 character ('&').
     *
     * @param string $name The name to look up.
     *
     * @return string The character sequence. In UTF-8 this may be more than one byte.
     */
    public static function lookupName($name) {
        // Do we really want to return NULL here? or FFFD
        return isset(Entities::$byName[$name]) ? Entities::$byName[$name] : null;
    }
    
    /**
     * Given a decimal number, return the UTF-8 character.
     *
     * @param $int
     *
     * @return false|string|string[]|null
     */
    public static function lookupDecimal($int) {
        $entity = '&#' . $int . ';';
        // UNTESTED: This may fail on some planes. Couldn't find full documentation
        // on the value of the mask array.
        return mb_decode_numericentity($entity, static::$numeric_mask, 'utf-8');
    }
    
    /**
     * Given a hexidecimal number, return the UTF-8 character.
     *
     * @param $hexdec
     *
     * @return false|string|string[]|null
     */
    public static function lookupHex($hexdec) {
        return static::lookupDecimal(hexdec($hexdec));
    }

}