When this value is set to a non-null-value it's value is used as php's
error_reporting level inside of
display() and fetch().
Smarty 3.1.2 introduced the
muteExpectedErrors() function. Calling
\Smarty\Smarty::muteExpectedErrors(); after setting up custom error handling
will ensure that warnings and notices (deliberately) produced by Smarty
will not be passed to other custom error handlers. If your error logs
are filling up with warnings regarding filemtime() or unlink()
calls, please enable Smarty's error muting.
See also debugging and troubleshooting.