Enabling chroot will put the Apache process that is handling the request into a chroot jail.
The usual caveats apply when running a process in a chrooted environment. Here are some things to bear in mind when using chroot with mod_vhostx.
mail() function does not work as it depends on the sendmail binary being inside the chroot. A quick search on Google shows several ways around this.
Connecting to localhost MySQL/PostgreSQL should be done via TCP rather than Unix socket
Perl requires all libraries to be installed under the chroot dir e.g. the contents of
/usr/share/perl5
/usr/lib64/perl5