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::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.