I think most anyone who compiles their software from scratch has run into this problem: They want to re-compile but can’t remember what configure options they used.
For PHP, you can use phpinfo(), but what about Apache? Or OpenSSL? Or APC?
It turns out that most packages create a config.nice when you compile them that contains all the options you picked. To recompile with the same options, just run ./config.nice instead of ./configure. You can also edit that file to change your options, or just copy/paste the contents directly to the command line.