This is plain 4.0.1pl2 in CGI mode on a RedHat 6.1 (patched up) sytem, however with Apache 1.3.3 (admitted, its oldish).
Setup is plain ./configure without any further options.

Whenever trying run a php4 script on that machine, php crashes (and httpd displays the preliminary end of script
error message).

Researching the problem showed:

It crashes in zend_alloc.c:289 (_estrdup)
called by cgi_main Line 632 trying to estrdup the PATH_TRANSLATED environment variable. Since that environment
variable is not set (this part I blame to my old apache)
it tries to strlen(0) (as thats what was returned by getenv)
and therefore segfaults.

Verified that by putting a wrapper around the scrip that would set the PATH_TRANSLATED variable, and voila, all went OK.

While I admit that in part this problem is caused by
the old apache, I also hold that no program should ever segfault, in particularly no attack-exposed program like
PHP.