I was only able to compile Apache w/ PHP as a static module (on HP-UX 11 using GCC) after modifying the function zend_extension_startup in the Zend/zend_extensions.c file to include preprocessor lines concerning conditional support of Zend extensions. Modified code looks like this:

static void zend_extension_startup(zend_extension *extension)
{
    /* following line added */
    #if ZEND_EXTENSIONS_SUPPORT
    if(extension->startup) {
        if(extension->startup(extension)!=SUCCESS) {
            DL_UNLOAD(extension->handle)
        }
    }
    /* following line added */
    #endif
}
 Before adding these lines I got the following error message when running make install on Apache after creating PHP as a static module:

/usr/ccs/bin/ld: Unsatisfied symbols:
  DL_UNLOAD (code)
collect2: ld returned 1 exit status
*** Error exit code 1

Stop.
*** Error exit code 1

Stop.
*** Error exit code 1

Stop.