What's the point of decaf??

The following warnings occurred:

Warning [2] Undefined property: MyLanguage::$bottomlinks_returncontent - Line: 6 - File: global.php(1070) : eval()'d code PHP 8.4.12 (Linux)

File	Line	Function
/inc/class_error.php	157	errorHandler->error
/global.php(1070) : eval()'d code	6	errorHandler->error_callback
/global.php	1070	eval
/misc.php	21	require_once