Here is the information of my php installation:
OS: centos 4.2, apache server 2.2.0, PHP: 5.1.2
apache is running correctly without php,

I compiled php's source code as follows:
./configure --with-apxs2 path-of-apxs --with-mysql path-of-mysql
make
make install

then created php.ini from php.ini-recommend (came with the source code)
modified httpd.conf and here is what I have in httpd.conf:
LoadModule php5_module modules/libphp5.so
AddModule mod_php5.c

<IfModule dir_module>
DirectoryIndex index.php default.php index.html index.htm
</IfModule>

AddType application/x-httpd-php .php .php3

Then, I tried to start apache but got an error message:
httpd: Syntax error on line 53 of /usr/local/apache2/conf/httpd.conf:
Cannot load /usr/local/apache2/modules/libphp5.so into server: /usr/local/apache2/modules/libphp5.so: undefined symbol: zend_register_list_destructors_ex

It seems like a code problem, but I am not sure and have no
clue whether I could debug it by looking into the code.
Maybe there is an easy solution from you guys.
I googled but got no useful information :-(

Appreciate your help.

looks like zend-engine isn't configure properly

this is my configure options of php for my slackware box
try to modifie this to your needs and compile it again

EXTENSION_DIR=/usr/lib/php/extensions
./configure \
--with-apxs2=/usr/sbin/apxs \
--enable-force-cgi-redirect \
--enable-fastcgi \
--with-ncurses \
--with-readline \
--prefix=/usr \
--enable-discard-path \
--with-config-file-path=/etc/apache2 \
--with-openssl \
--with-zlib=/usr \
--enable-bcmath \
--with-bz2 \
--with-pic \
--enable-calendar \
--enable-ctype \
--with-curl=shared \
--enable-dba=shared \
--with-gdbm \
--with-db3 \
--with-inifile \
--with-flatfile \
--enable-dio \
--enable-ftp \
--with-gd=/usr \
--enable-gd-native-ttf \
--with-jpeg-dir=/usr \
--with-png-dir=/usr \
--with-freetype-dir=/usr \
--with-gettext=/usr \
--with-gmp=shared \
--with-mbstring \
--with-mcrypt=/usr \
--with-mime-magic \
--with-mysql=/usr \
--with-mysql-sock=/var/run/mysql/ \
--without-mysqli \
--with-pspell=/usr \
--enable-shmop \
--enable-soap \
--enable-sockets \
--with-regex=php \
--enable-sysvmsg \
--enable-sysvsem \
--enable-sysvshm \
--enable-wddx \
--enable-xml \
--with-libxml-dir=/usr \
--with-xsl=/usr \
--with-pear \
--enable-inline-optimization \
--enable-memory-limit \
--enable-zend-multibyte \
--enable-shared \
--disable-static \
--disable-debug \

Thanks very much.
I tried to recompile PHP with more options
and it worked this time
Still don't know why this would be the case though.