I am running IBM_HTTP_SERVER/1.3.19 powered by Apache/1.3.20 and am having problems installing PHP as a loadable module of Apache. 

Method 1:

I installed php-4.0.4pl1-9.i386.rpm and copied  /usr/lib/apache/libphp4.so to the apache libexec directory.

I then edited the httpd.conf file by adding the following:
  LoadModule php4_module libexec/libphp4.so
  AddType application/x-httpd-php .php4 .php3 .phtml .php
When I try to restart the server, it cannot be started and I get the following message:

API module structure 'php4_module' in file ... is garbled - perhaps this is not an Apache module DSO? 

Method 2:
Compiling PHP source code and using apxs.

the Apache does allow for DSO loading
httpd -l lists
  http_core.c
  mod_so.c

./configure --prefix=/usr/local/php --with-apxs=/opt/IBMHTTPServer/bin/apxs
make

this ends with the following error:

make[3]: Entering directory `/tmp/php-4.0.6/sapi/apache'
/bin/sh /tmp/php-4.0.6/libtool --silent --mode=compile gcc  -I. -I/tmp/php-4.0.6/sapi/apache -I/tmp/php-4.0.6/main -I/tmp/php-4.0.6 -I/opt/IBMHTTPServer/include -I/tmp/php-4.0.6/Zend -I/tmp/php-4.0.6/ext/mysql/libmysql -I/tmp/php-4.0.6/ext/xml/expat/xmltok -I/tmp/php-4.0.6/ext/xml/expat/xmlparse -I/tmp/php-4.0.6/TSRM  -DLINUX=22 -DUSE_HSREGEX -DUSE_EXPAT -DSUPPORT_UTF8 -DXML_BYTE_ORDER=12 -g -O2  -c sapi_apache.c
In file included from /opt/IBMHTTPServer/include/ap_config.h:114,
                 from /opt/IBMHTTPServer/include/httpd.h:72,
                 from sapi_apache.c:32:
/opt/IBMHTTPServer/include/os.h:82:23: os-inline.c: No such file or directory
make[3]: *** [sapi_apache.lo] Error 1
make[3]: Leaving directory `/tmp/php-4.0.6/sapi/apache'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/tmp/php-4.0.6/sapi/apache'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/tmp/php-4.0.6/sapi'
make: *** [all-recursive] Error 1


Any help would be appreciated, Thanks!