Can't make PHP 4.2.1 with Apache2

I am trying to compile PHP 4.2.1 with mysql and Apache 2 using gcc on Solaris 2.7. After $ ./configure --with-mysql --with-apxs2=/usr/local/apache2/bin/apxs and $ make I get: Making all in Zend make[1]: Entering directory `/home/jon/php-4.2.1/Zend' /bin/sh ../libtool --silent --mode=compile gcc -DHAVE_CONFIG_H -I. -I. -I../main -D_POSIX_PTHREAD_SEMANTICS -D_POSIX_ PTHREAD_SEMANTICS -D_REENTRANT -I../TSRM -DTHREAD=1 -g -O2 -pthreads -DZTS -prefer-pic -c -o zend_language_parser.lo `test -f zend_language_parser.c || echo './'`zend_language_parser.c In file included from zend_compile.h:24, from zend_language_parser.c:147: zend.h:55: unix.h: No such file or directory make[1]: *** [zend_language_parser.lo] Error 1 make[1]: Leaving directory `/home/jon/php-4.2.1/Zend' make: *** [all-recursive] Error 1 It is certainly true that the file "unix.h" is nowhere on the system. Should it be? I would be grateful if anyone who knows what's going on could help me. Jon