Under heavy load, mod_php4 seems to corrupt constants, and fail to require php file specified in a constant. It leaves the following error message in apache error_log:

[Tue Nov 26 15:02:47 2002] [error] PHP Fatal error:  Failed opening required 'onmassdeletepost' (include_path='.:/usr/local/lib/php'
) in /usr/home/huasing/public_html/common.php on line 35
[Tue Nov 26 15:02:48 2002] [error] PHP Fatal error:  Failed opening required 'DB_ERROR_VALUE_COUNT_ON_ROW' (include_path='.:/usr/loc
al/lib/php') in /usr/home/huasing/public_html/common.php on line 35
[Tue Nov 26 15:02:49 2002] [error] PHP Fatal error:  Failed opening required '_PEAR_default_error_options' (include_path='.:/usr/loc
al/lib/php') in /usr/home/huasing/public_html/common.php on line 35

The relevant lines in common.php are:
33 require_once('/home/home/lib/common/config.php');

34 require_once('PEAR.php');
35 require_once('DB.php');
36 require_once(HUASING_LIB_ERROR);
37 require_once(HUASING_LIB_ENV);

After turning off KeepAlive in apache, and set MaxRequestsPerChild = 1 , this problem doesn't appear any more.

Configure:
'./configure' '--with-apxs=/usr/local/sbin/apxs' '--with-config-file-path=/usr/local/etc' '--enable-versioning' '--with-regex=system' '--without-gd' '--without-mysql' '--with-gd=/usr/local' '--enable-gd-native-ttf' '--with-freetype-dir=/usr/local' '--with-jpeg-dir=/usr/local' '--with-png-dir=/usr/local' '--with-zlib' '--with-mysql=/usr/local' '--enable-xslt' '--with-xslt-sablot' '--with-expat-dir=/usr/local' '--with-iconv=/usr/local' '--prefix=/usr/local' 'i386-portbld-freebsd4.6.2'

it runs on a Dual CPU server.