html compatibility of global variables

[Little-Ben]

Consider html compatibility of "global variables" like $owner string and others.
Needs to be surrounded by htmlentities() or something similar, if strings are inserted into html.
Otherwise ' or " (and others) might cause trouble.

e.g. search for $owner
find /path/to/ChurchRota/ -type f -print | xargs egrep '$owner'

[sgreenslade]

Some old, but useful advice here on checking input from users:
https://www.dreamhost.com/blog/2013/05/22/php-security-user-validation-and-sanitization-for-the-beginner/