On Sequent Dynix/Ptx 4.4.4 sed needs extra help recognizing an escaped escape character preceding "n" in a substitution rule in genif.sh.  This causes internal_functions.c to be generated with "backslash-enn" literals still embedded, leading to compiler errors.  Here is the symptom.  A hackaround that works on this platform follows at the very end.

        cc -DHAVE_CONFIG_H -I. -I/opt/apache_1.3.12/php-4.0.0/ -I/opt/apache_1.3.12/php-4.0.0 -I/opt/apache_1.3.12/php-4.0.0/Zend -I/opt/apache_1.3.12/php-4.0.0 -I/opt/apache_1.3.12/php-4.0.0/ext/mysql/libmysql -I/opt/apache_1.3.12/php-4.0.0/ext/xml/expat/xmltok -I/opt/apache_1.3.12/php-4.0.0/ext/xml/expat/xmlparse  -DXML_BYTE_ORDER=12 -Wc,+abi-socket -g  -c internal_functions.c && touch internal_functions.lo
"internal_functions.c", line 32: warning: tokens ignored at end of directive line
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: undefined symbol: n
"internal_functions.c", line 38: warning: improper pointer/integer combination: op "="
"internal_functions.c", line 38: non-constant initializer: op "NAME"
"internal_functions.c", line 38: syntax error before or at: phpext_standard_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: identifier redeclared: n
"internal_functions.c", line 38: syntax error before or at: phpext_session_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: syntax error before or at: phpext_posix_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: syntax error before or at: phpext_pcre_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: syntax error before or at: phpext_mysql_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: syntax error before or at: phpext_db_ptr
"internal_functions.c", line 38: warning: old-style declaration; add "int"
"internal_functions.c", line 38: invalid source character: '\'
"internal_functions.c", line 39: warning: old-style declaration; add "int"
"internal_functions.c", line 39: syntax error before or at: }
"internal_functions.c", line 39: warning: syntax error:  empty declaration
"internal_functions.c", line 46: warning: null dimension: sizeof()
"internal_functions.c", line 51: warning: null dimension: sizeof()
"internal_functions.c", line 56: warning: null dimension: sizeof()
*** Error code 1
Make: .  Stop.
*** Error code 1
Make: .  Stop.
%

Here is the hackaround, a tiny change I made to restore proper function.  Whether genif.sh will work on other platforms with this in place is unknown.

Change line 39-40 of genif.sh from this substitution rule

<        -e 's/\\n/\
</g'

to this

>        -e 's/[\\]n/\
>/g'

This evidently stops Sequent's sed from trying so hard to recognize a newline pattern.  The original syntax substituted the input line's actual newline for a new newline on my system, ignoring the embedded "\n".

If you make this change to genif.sh _after_ seeing the above error, you must "rm internal_functions.c" before rerunning make.