Calling xml_parser causes a SegFault. Confirmed on a simple
example from documentation on two different machines running
different apache versions, but same 4.0.4.

SuSE gdb:

#0  0x40184635 in call_user_function_ex () at
zend_execute_API.c:102
#1  0x4018448c in call_user_function () at
zend_execute_API.c:102
#2  0x40207375 in xml_call_handler (parser=0x814f394,
handler=0x813e464,
    argc=3, argv=0xbfffc0a0) at xml.c:361
#3  0x40207bbb in _xml_startElementHandler () at xml.c:604
#4  0x4020b8c7 in doContent (parser=0x813b630, startTagLevel=0,
    enc=0x4024a3c0,
    s=0x815d44a "<quizset>\n<quiztitle>Sample
quiz</quiztitle>\n<questionsets>\n<questionset
id=\"0\">\n<question>Roses are red, violets
are</question>\n<answerset>\n<answer>scarlet</answer>\n<answer
correct=\"yes\">blue</answer"...,
    end=0x815d932 "", nextPtr=0xbfffc228) at xmlparse.c:1268
#5  0x4020b082 in contentProcessor (parser=0x813b630,
    start=0x815d44a "<quizset>\n<quiztitle>Sample
quiz</quiztitle>\n<questionsets>\n<questionset
id=\"0\">\n<question>Roses are red, violets
are</question>\n<answerset>\n<answer>scarlet</answer>\n<answer
correct=\"yes\">blue</answer"...,
    end=0x815d932 "", endPtr=0xbfffc228) at xmlparse.c:957
#6  0x4020d0a6 in prologProcessor (parser=0x813b630,
    s=0x815d44a "<quizset>\n<quiztitle>Sample
quiz</quiztitle>\n<questionsets>\n<questionset
id=\"0\">\n<question>Roses are red, violets
are</question>\n<answerset>\n<answer>scarlet</answer>\n<answer
correct=\"yes\">blue</answer"...,
    end=0x815d932 "", nextPtr=0xbfffc228) at xmlparse.c:2036
#7  0x4020cda5 in prologInitProcessor (parser=0x813b630,
    s=0x815d434 "<?xml
version=\"1.0\"?>\n<quizset>\n<quiztitle>Sample
quiz</quiztitle>\n<questionsets>\n<questionset
id=\"0\">\n<question>Roses are red, violets
are</question>\n<answerset>\n<answer>scarlet</answer>\n<answer
corr"...,
    end=0x815d932 "", nextPtr=0xbfffc228) at xmlparse.c:1967
#8  0x4020abab in php_XML_Parse () at xmlparse.c:596
#9  0x4020912d in php_if_xml_parse () at xml.c:604
#10 0x4017e179 in execute () at ./zend_execute.c:877
#11 0x4018065a in execute () at ./zend_execute.c:877
#12 0x4018065a in execute () at ./zend_execute.c:877
#13 0x4018065a in execute () at ./zend_execute.c:877
#14 0x4018cfb6 in zend_execute_scripts () at zend.c:258
#15 0x4019fc44 in php_execute_script () at main.c:1153
#16 0x4019bf10 in apache_php_module_main () at sapi_apache.c:98
#17 0x4019c939 in send_php () at mod_php4.c:433
#18 0x4019c983 in send_parsed_php () at mod_php4.c:433
#19 0x806c259 in ap_invoke_handler ()
#20 0x80814cf in process_request_internal ()
#21 0x8081542 in ap_process_request ()
#22 0x80783e6 in child_main ()
#23 0x80785a5 in make_child ()
#24 0x8078726 in startup_children ()
#25 0x8078d9d in standalone_main ()
#26 0x80795cc in main ()
#27 0x40087a8e in __libc_start_main () at
../sysdeps/generic/libc-start.c:93

configure line:

./configure --with-apxs=/usr/local/apache/bin/apxs
--with-mysql=/usr --with-dom=/usr/local/dom2 --enable-track-vars