Please add your configure line to this bug report.

It's a long one :)
As I am currently still trying to get libpdf to become a nice loadable extension for php...

The part where it probably revolves around for this problem:
--with-sybase-ct=shared,/usr

./configure --enable-versioning --prefix=/usr --with-apxs=/usr/bin/apxs --with-regex=system --with-config-file-path=/etc/php4/apache --disable-rpath --disable-debug --enable-memory-limit --enable-calendar --enable-sysvsem --enable-sysvshm --enable-track-vars --enable-trans-sid --enable-bcmath --with-bz2 --enable-ctype --with-db2 --with-iconv --with-ndbm --enable-exif --enable-filepro --enable-ftp --with-gettext --enable-mbstring --enable-mbstr-enc-trans --with-pcre-regex=/usr --enable-shmop --enable-sockets --enable-wddx --with-xml=/usr --with-expat-dir=/usr --enable-yp --with-zlib --with-pgsql --disable-static --with-layout=GNU --with-curl=shared,/usr --with-dom=shared,/usr --with-zlib-dir=/usr --with-gd=shared,/usr --with-gd-dir=/usr --with-jpeg-dir=shared,/usr --with-xpm-dir=shared,/usr/X11R6 --with-png-dir=shared,/usr --with-freetype-dir=shared,/usr --with-imap-ssl=shared,/usr --with-ldap=shared,/usr --with-mcal=shared,/usr --with-mhash=shared,/usr --with-mm --with-mysql=shared,/usr --with-recode=shared,/usr --with-snmp=shared --with-sybase-ct=shared,/usr --with-ttf=shared,/usr --with-t1lib=shared,/usr --with-pdflib=shared,/tmp/pdflib-4.0.1/bind/c/ --with-tiff-dir=/usr

After adding the include (installing the freetds-dev package) it worked... but then still the configure script should have warned before that.

I added a check for this to not continue the configure
if ctpublic.h is not found.

--Jani