This works on all versions of Apache webserver greater than 2.2.10.
I’ll presume you have a current working version of Apache serving files from /var/www/

mkdir -p /chroot/var/ 

Required for PHP5 compatibility:

mkdir -p /chroot/var/lib/php5
chown root:www-data /chroot/var/lib/php5
chmod 770 /chroot/var/lib/php5
cp /etc/localtime /chroot/etc/localtime
cp -R /usr/share/zoneinfo /chroot/usr/share/zoneinfo
cp -R /usr/share/apache2 /chroot/usr/share/apache2 

mv /var/www /chroot/var/ 

To help with compatibility and user / sysadmin expectations

ln -s /chroot/var/www /var/www 

Enable Apache’s in-built chroot (Debian)

echo "ChrootDir /chroot" > /etc/apache2/conf.d/chroot 

Enable Apache’s in-built chroot (Redhat/CentOS/Fedora)

echo "ChrootDir /chroot" >> /etc/httpd/conf/httpd.conf 
semanage fcontext -a -t httpd_sys_content_t “/chroot/var/www(/.*)?”

service apache2 restart 

Now test your damn website! Logfiles are your friend for troubleshooting any bugs :-)