Hi, I got this symptom by compiling PHP:
xlc  -I. -I/home/pistoor/php-4.0.4pl1/main -I/home/pistoor/php-4.0.4pl1/main -I/home/pistoor/php-4.0.4pl1 -I/home/pistoor/php-4.0.4pl1/Zend -I/home/pistoor/php-4.0.4pl1/ext/mysql/libmysql -I/home/pistoor/php-4.0.4pl1/ext/xml/expat/xmltok -I/home/pistoor/php-4.0.4pl1/ext/xml/expat/xmlparse -I/home/pistoor/php-4.0.4pl1/TSRM  -DXML_BYTE_ORDER=21 -qsource -qshowinc -I/home/pistoor  -c internal_functions.c && touch internal_functions.lo
"/usr/include/sys/vnode.h", line 102.9: 1506-213 (S) Macro name V_RENAME cannot be redefined.
"/usr/include/sys/vnode.h", line 102.9: 1506-358 (I) "V_RENAME" is defined on line 190 of /home/pistoor/php-4.0.4pl1/TSRM/tsrm_virtual_cwd.h.

 I use the xlc-version of the C Set ++ for AIX compiler, as it is more ANSI-C than the cc-version. It also shows more errors.
 My configuration of PHP (as a CGI-program to be used by Lynx):
CC=xlc ./configure --prefix=/home/pistoor/php \
  --with-config-file-path=/home/pistoor/php --enable-debug \
  --enable-sigchild --enable-calendar --enable-ftp \
  --enable-trans-sid --enable-shmop --with-regex=php \
  --enable-sysvsem --enable-sysvshm --enable-wddx \
  --enable-yp

The file /usr/include/sys/vnode.h got included via /usr/include/sys/shm.h and others by php_sysvshm.h. So I have protected this include against redefining V_RENAME:
#ifdef V_RENAME
#define PHP_V_RENAME V_RENAME
#undef V_RENAME
#endif

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#ifdef PHP_V_RENAME
#ifdef V_RENAME
#undef V_RENAME
#endif
#define V_RENAME PHP_V_RENAME
#undef PHP_V_RENAME
#endif

 Regard
 Andreas Pistoor