Can't add new payment option

-- HikaShop version -- : 6.1.1
-- Joomla version -- : 5.4.0
-- Error-message(debug-mod must be tuned on) -- : Compile Error: Array and string offset access syntax with curly braces is no longer supported

Hello,

I recently got the warning message "Your PayPal payment method is obsolete and will soon be discontinued by PayPal. Please go in the System>Payment methods menu, click on the 'new' button and select the 'HikaShop PayPal Checkout payment plugin' to configure the PayPal Checkout payment method which is now replacing it. Once done and the new PayPal Checkout payment method is available on your website, disable the old PayPal payment method and this error message will disappear."
I tried following these guidelines, but got a Joomla error page. I updated HikaShop to the latest version, but the problem persisted. After switching on debugging, I saw that it's a PHP error:

Compile Error: Array and string offset access syntax with curly braces is no longer supported

The code is:

public static function getScriptNameFromUrl ( $url )
{
$path = parse_url($url, PHP_URL_PATH);
$len = strlen($path);
if ( $len == 0 || '/' == $path{$len-1} ) {
return "";
}
return basename($path);
}

coming form /homepages/3/d522575378/htdocs/joomla-2014-04-07/plugins/hikashoppayment/platron/PG_Signature.php:17

(N.B.: I was able to fix this issue because I also have ssh access to the site. I simply edited the PHP code mentioned in the exception report, and replaced the curly braces by normal [] indexing. This way, I was able to continue. But perhaps this should be fixed in an upcoming version to ensure PHP compatibility?)