At the end of configure I get the error message:

checking whether to include zlib support... yes
checking for gzgets in -lz... no
configure: error: Zlib module requires zlib >= 1.0.9.

zlib is not the problem.  As config.log shows

configure:38170: gcc -o conftest -g -O2  -D_POSIX_PTHREAD_SEMANTICS -DXML_BYTE_ORDER=21 -L/opt/gnu/lib  -R/usr/ucblib -L/usr/ucblib -R/opt/gnu/lib -L/opt/gnu/lib -R/usr/local/lib -L/usr/local/lib -R/opt/serv/lib -L/opt/serv/lib -R/opt/mysql/lib/mysql -L/opt/mysql/lib/mysql conftest.c -lz  -lpq -lmysqlclient -lttf -lgd -ldb -lgdbm -lresolv -lresolv -lm -ldl -lcrypt -lnsl -lsocket  -lsocket 1>&5
Undefined			first referenced
 symbol  			    in file
png_set_strip_16                    /opt/serv/lib/libgd.so
png_set_read_fn                     /opt/serv/lib/libgd.so
...


I use 

./configure --with-apxs=/opt/serv/sbin/apxs --enable-versioning --with-mysql=/opt/mysql --prefix=/opt/php --with-exec-dir=/opt/serv/libexec/ --with-db2 --with-gd  --with-ttf=/opt/serv --with-ldap=/opt/serv --with-zlib=/opt/gnu --with-pgsql=/opt/serv --enable-sysvsem --enable-sysvshm --with-yp --enable-ftp --with-config-file-path=/opt/php/etc --with-gdbm=/opt/gnu

Fixed by changing the configure script:

  LIBS="-lgd $LIBS"

into
  
   LIBS="-lgd -lpng $LIBS"



Originally I didn`t log this as I thought it was similar to bug #4423 -
according to the reports this was fixed in 4.0.1.