I followed the instructions in the INSTALL file for a static module build for Apache 1.3.12.

After doing a configure with the listed options + "--prefix=/var/httpd" I ran make (GNU make 3.75) to build PHP4 RC1. Compilation failed in zend_execute.c:

/bin/sh ../libtool --silent --mode=compile cc -DHAVE_CONFIG_H -I. -I. -I..  -DXML_BYTE_ORDER=21 -D_POSIX_THREAD_SAFE_FUNCTIONS -g -c ./zend_execute.c
"./zend_execute.c", line 84: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 88: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 103: warning(1110): statement is unreachable
                                                break;
                                                ^

"./zend_execute.c", line 124: warning(1110): statement is unreachable
                                                break;
                                                ^

"./zend_execute.c", line 131: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 143: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 156: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 159: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 744: warning(1110): statement is unreachable
                        break;
                        ^

"./zend_execute.c", line 1340: warning(1110): statement is unreachable
                                break;
                                ^

"./zend_execute.c", line 1386: warning(1110): statement is unreachable
                                break;
                                ^

"./zend_execute.c", line 1705: warning(1110): statement is unreachable
                                break;
                                ^

"./zend_execute.c", line 1877: warning(1110): statement is unreachable
                                NEXT_OPCODE();
                                ^

"./zend_execute.h", line 49: error(1113): function "safe_free_zval_ptr" was
          referenced but not defined
  ZEND_API inline void safe_free_zval_ptr(zval *p);
                       ^

"./zend_execute.h", line 51: error(1113): function "i_zend_is_true" was
          referenced but not defined
  ZEND_API inline int i_zend_is_true(zval *op);
                      ^

"./zend_execute.h", line 53: error(1113): function
          "zend_assign_to_variable_reference" was referenced but not defined
  ZEND_API inline void zend_assign_to_variable_reference(znode *result, zval **variable_ptr_ptr, zval **value_ptr_ptr, temp_variable *Ts ELS_DC);
                       ^

"./zend_execute.h", line 56: error(1113): function
          "zend_ptr_stack_clear_multiple" was referenced but not defined
  ZEND_API inline void zend_ptr_stack_clear_multiple(ELS_D);
                       ^

"./zend_execute.h", line 57: error(1113): function "zend_ptr_stack_get_arg"
          was referenced but not defined
  ZEND_API inline int zend_ptr_stack_get_arg(int requested_arg, void **data ELS_DC);
                      ^

5 errors detected in the compilation of "./zend_execute.c".
make[1]: *** [zend_execute.lo] Error 1

I am using the SGI MIPSpro C/C++ compilers, version 7.2.1.4.