Description:
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configure creates a cache file in ..; specifically ../config.cache.

I'm not thrilled about a build touching a directory above itself - this is not good practice, as the containing directory is often shared among many products.

However, PHP even creates trouble for itself, since it caches paths.

For example, consider an upgrade from PHP 5.4.7 to 5.6.30 or 7.1.4.

Burried in the configure script (after debugging various weird symptoms - compile and/or link failures):

checking for PDO includes... (cached) /home/litt/kits/php-5.4.7/ext

configure is using the result of a different version.

I strongly suggest that the configure .cache file be put in a subdirectory of the kit.  I understand why ../ was chosen - it allows one to wipe out the kit directory, untar cleanly, and still use the cache.  And if one has a common directory for php extensions, arguably they can use the same cache.  But the side effect is bad, and quite unexpected; starting over should START OVER!.

If you must have a sticky cache, or believe its benefits outweigh the risks, how about changing the file name?  E.g. php-5.4.7-config.cache

At least this would prevent versions of PHP from conflicing with each-other - and with other products...

Thanks.