Fix "Undefined index: USER" error from #127
constant('SID')

ISSUE-82 - (continuation of) Fix odd PHP quirk which triggers fatal error "Allowed memory size of --- bytes exhausted" when accessing SID constant
(adding to zc_install for consistency)
Merge pull request #159 from drbyte/issue-82

constant('SID')
Merge pull request #154 from drbyte/undefined-index-user

Fix "Undefined index: USER" error from #127