Description:
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I've an apache-2.0.47 setup with several vhosts, using mpm_prefork

Some scripts when they load will throw file-not-found errors, because requires fail as the include path may be set to, instead of ".:/usr/share/pear", things like "<garbage>pear", "<garbage>.:/usr/share/pear", "<garbage>are/pear<garbage>"

It acts like threads stepping on each other, but I'm using mpm_prefork.

My mega-configure line is:
 
'./configure' 'LDFLAGS=-s' 'CFLAGS=-O2 -march=athlon -DEAPI=1 -I/usr/X11R6/include' 'CXXFLAGS=-O2 -march=athlon' 'FFLAGS=-O2 -march=athlon' 'CPPFLAGS=' 'CC=athlon-pld-linux-gcc' 'CXX=athlon-pld-linux-g++' '--build=athlon-pld-linux' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc/php' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib' '--libexecdir=/usr/lib' '--localstatedir=/var' '--sharedstatedir=/var/lib' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--with-apxs2=/usr/sbin/apxs' '--with-config-file-path=/etc/php' '--with-exec-dir=/usr/bin' '--disable-debug' '--enable-memory-limit' '--enable-bcmath=shared' '--enable-calendar=shared' '--enable-ctype=shared' '--enable-dba=shared' '--enable-dbx=shared' '--enable-dio=shared' '--enable-exif=shared' '--enable-ftp=shared' '--enable-gd-native-ttf' '--enable-magic-quotes' '--enable-mbstring=shared' '--disable-mbstr-enc-trans' '--enable-mbregex' '--enable-overload=shared' '--disable-pcntl' '--enable-posix=shared' '--enable-session' '--enable-shared' '--enable-shmop=shared' '--enable-sysvsem=shared' '--enable-sysvshm=shared' '--enable-track-vars' '--enable-trans-sid' '--enable-safe-mode' '--enable-sockets=shared' '--enable-ucd-snmp-hack' '--enable-wddx=shared' '--enable-xml=shared' '--enable-xslt=shared' '--enable-yp=shared' '--with-bz2=shared' '--with-cpdflib=shared' '--with-crack=shared' '--with-curl=shared' '--with-db' '--with-db4' '--with-dbase=shared' '--with-dom=shared' '--with-dom-xslt=shared' '--with-dom-exslt=shared' '--with-expat-dir=shared,/usr' '--with-iconv=shared' '--with-filepro=shared' '--with-freetype-dir=shared' '--with-gettext=shared' '--with-gd=shared,/usr' '--with-gdbm' '--with-gmp=shared' '--with-hyperwave=shared' '--with-imap=shared' '--with-imap-ssl' '--with-interbase=shared,/usr' '--with-jpeg-dir=shared,/usr' '--with-ldap=shared' '--with-mcal=shared,/usr' '--with-mcrypt=shared' '--with-mhash=shared' '--with-ming=shared' '--with-mnogosearch=shared,/usr' '--with-msession=shared' '--with-mysql=shared,/usr' '--with-mysql-sock=/var/lib/mysql/mysql.sock' '--with-openssl' '--with-pcre-regex=shared' '--with-pdflib=shared' '--with-pear=/usr/share/pear' '--with-pgsql=shared,/usr' '--with-png-dir=shared,/usr' '--with-pspell=shared' '--with-regex=php' '--without-sablot-js' '--with-snmp=shared' '--with-sybase-ct=shared,/usr' '--with-t1lib=shared' '--with-tiff-dir=shared,/usr' '--with-unixODBC=shared' '--with-xmlrpc=shared,/usr' '--with-xslt-sablot=shared' '--with-yaz=shared' '--with-zip=shared' '--with-zlib=shared' '--with-zlib-dir=shared,/usr'

Though the actual modules being used are fairly small in the cases I've seen the bug show up: imap, mysql, pcre, pspell are the ones that come to mind.

Reproduce code:
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Can't reproduce reliably, but IMP from the Horde project will trigger it, as well as TWIG from http://twig.screwdriver.net