configure created with buildconf does not show unknown options

So I'm installing PHP 5.2.10. I run configure with the same options I had for 5.0. At the end it complains about some unknown options. I'll just use two examples "--enable-yp" and "--with-pdflib=/usr/local/share/pdflib/bind/c' Now I downloaded and extrated pdf from pecl and put it in ext/pdf. I didn't do anything about yp tho. Next I removed configure and ran "buildconf --force" Then I ran the new configure with the exact same options as before. As expected it didn't complain about "--with-pdflib=/usr/local/share/pdflib/bind/c' however since I did nothing about yp, I shouldn't I have gotten another error message about "--enable-yp" being an unknown option? There were also a number of other options that should have been unknown I've omitted them in the interest of brevity. Is there something I can do with buildconf that will make the new configure tell me about unknown options? Thanks in advance.