Is there any way in which we can upgrade PHP without affecting the current extensions.
We had upgraded from php 5.3.25 to php 5.6.7 on dev environment, after this some extensions did not work.
We have a site which uses memcached extension, while upgrade if this extension gets affected then the site will go down which we need to avoid. So we need to keep the memcached as is and upgrade PHP.
I'd suggest when you upgrade to build your PHP version with all the extensions that you need. Otherwise there is no way you know the extensions are still compatible or not.