Thread:Project:Support desk/Error running the update script/reply (21)

PCRE is a library, which is usually part of your system (on Linux at least). PHP is compiled with links to that library. To install a different version of PCRE you should usually install it (read installation instructions of that library) and then recompile PHP.

But usually you won't need that, and just upgrade your MediaWiki, or apply the patch that solved that problem.