Use double quotes instead of single
Return sanity, fewer exits, and do not store database crediential (read direct from connect.ini)

Removed all private vars relating to login. Now use a two vars within
the scope of __construct. One is the contents of connect.ini, the other is
a string to pass when constructing new PDO.

Fewer exits/dies (only exit on fail to connect), and use try/catch to avoid
errors containing database credentials.

Removed all DB_ prefixes for methods.

slq_table now tries to avoid a second query and gets table headers from
results of first query, if any. If it is an empty array, then it does the
second query to get the headers.
Documentation for json_response, change error_reporting levels, CSP after nonce
Toggle class now functions, added attributeFilter to $().watch()