We've got the same problem described on #5206.
Here what we've done to make it work:

Edited Zend/zend-parser.y and added the following line:
#include "zend_globals_macros.h"

Maybe the Iplanet 4.1SP1 directory structure have changed, so we had
to make a link:

cd /usr/netscape/server4
ln -s plugins/include include

And finally, we had to edit sapi/nsapi/nsapi.c and add the line:
#define XP_UNIX 1
at the beginning of the file.

After these modifications, the compilation succeeded.