lookupHex example

                $hex = $this->scanner->getHex();
                if (empty($hex)) {
                    $this->parseError('Expected &#xHEX;, got &#x%s', $tok);
                    // We unconsume because we don't know what parser rules might                     // be in effect for the remaining chars. For example. '&#>'                     // might result in a specific parsing rule inside of tag                     // contexts, while not inside of pcdata context.                     $this->scanner->unconsume(2);

                    return '&';
                }
                $entity = CharacterReference::lookupHex($hex);
            }             // Decimal encoding.             // [0-9]+;             else {
                // Convert from decimal to char.                 $numeric = $this->scanner->getNumeric();
                if (false === $numeric) {
                    $this->parseError('Expected &#DIGITS;, got &#%s', $tok);
                    $this->scanner->unconsume(2);

                    return '&';
                }