To compile php on HP-UX 11.00. system (PA-RISK) SMP with gcc compiler, I followed these steps :
1. configure Apache with so, make, make install, test : It's OK
2. in php source directory : ./configure --with-apxs=/opt/apache/bin/apxs
At the make time I have an error 1 
Compilation in static mode works without pb...
Now I would like to upgrade to Apache2.0.39, static is not available, then I had to find a way to solve it...
From mailing list, and man pages here's the way I used :
1. change sapi/apache2filter/php_functions.c, replace "MODULE_MAGIC_AT_LEAST" to "AP_MODULE_MAGIC_AT_LEAST"
If I make, then I have another error with c_time_r and asctime_r from main/reentrancy.c.
To solve it, edit reentrancy.c :
Add "&& !defined(PHP_HPUX_TIME_R)" 
 at the end of these 4 lines : 
#if !defined(HAVE_LOCAL_TIME_R) && (defined(HAVE_LOCALTIME) 
#if !defined(HAVE_CTIME_R) && (defined(HAVE_CTIME) 
#if !defined(HAVE_ASCTIME_R) && (defined(HAVE_ASCTIME) 
#if !defined(HAVE_GMTIME_R) && (defined(HAVE_GMTIME) 

change the functions c_time_r : 
if (ctime_r(clock, buf, 26) != -1) 
to 
if (ctime_r(clock, buf) != -1) 
(2 times in this source file) 
Do the same with asctime_r : 
if (asctime_r(tm, buf, 26) != -1) 
to 
if (asctime_r(tm, buf) != -1) 
(2 times also). 

then make is OK, make install also.

last remark with OCI8 on HP-UX11.00 (not linked with the bug report), define LD_PRELOAD="/usr/lib/libcl.2" ; export LD_PRELOAD before running Apache (in case of version 2.0.39 multi thread).

Hope it will help