Left shift operation in PHP when upgrading from PHP5 to PHP 7

1<< -1 is OK for PHP 5, but fails for PHP 7.
Directly using 1<< -1 = -9223372036854775808
(Obtained from PHP Sandbox http://sandbox.onlinephpfunctions.com/)
/var/www/html/new6sp/application/controllers/ttr_view.php
line 781 change from               
        if($rcode < 33) {
            $code = 1 << $rcode;
            $r[$sid]['terms'][$term]['code'] |= $code;
        }else{
            $code = 1 << ($rcode-33);
            $r[$sid]['terms'][$term]['code_upper'] |= $code;
        }
to
        if($rcode < 0) {
            $code = -9223372036854775808;
            $r[$sid]['terms'][$term]['code'] |= $code;
        }               
        elseif($rcode < 33) {
            $code = 1 << $rcode;
            $r[$sid]['terms'][$term]['code'] |= $code;
        }else{
            $code = 1 << ($rcode-33);
            $r[$sid]['terms'][$term]['code_upper'] |= $code;
        }