Updating unmaintained package

Hello,

I am new to this list and don't feel (due to my non-existant C skills) 
to belong here, but I need a PECL package that is unmaintained and 
therefore not available for PHP 7: https://pecl.php.net/package/pcsc

I tried to compile it and it throws some errors where I feel somewhat 
confident that I can solve them. It seems like basic syntax changes. 
E.g. I found out that I had to replace |zend_rsrc_list_entry ||by 
|||zend_resource ||(following this blog post: 
http://www.sklar.com/software/php/2015/03/23/converting-a-php-extension-to-php-7/).

But there are other errors like "error: expected expression before" when 
calling ZEND_FETCH_RESOURCE or "error: macro "RETVAL_STRING" passed 2 
arguments, but takes just 1".

Seem to me like very basic things to solve, but I can't find any 
reference / manual where I can find the usage of these functions and 
which parameters the function expects. Can anybody give me some hints 
where to search for this information? Maybe there is also a migration 
guide for PHP extensions from PHP 5 to PHP 7 somewhere.

Best Regards,
Benedikt.