Binary versioning/compatibility of PECL modules

Hi, If I compile a PECL module, in what way(s) (if any) is it dependent on the version of PHP? Might future upgrades of PHP break it, forcing me to recompile? Or is it future-safe? An "ldd" doesn't seem to show anything that would superficially link it to the PHP version, but am I missing something? I have in mind RPM packaging in particular, where if (and only if) there is a dependency on something like a PHP version or API, I'd want to enumerate that somehow and incorporate it in the packaging. Thanks, Tim