PHP extensions in C are pretty rare since it's so hard to distribute them (outside a few exceptions that exist in common package management systems), so in that

PHP extensions in C are pretty rare since it's so hard to distribute them (outside a few exceptions that exist in common package management systems), so in that sense, I guess? But no, a PHP extension in C can have a memory leak like any other C code. It's not at all uncommon actually, since there are fewer consequences; CGI mode PHP cleans up after every request, FastCGI mode PHP by default restarts workers after a number of requests because of the class of effects (unwanted state) that includes memory leaks.