Description:
------------
From PHP manual: PHP_OUTPUT_HANDLER_CLEANABLE const control access to functions: ob_clean(), ob_end_clean(), and ob_get_clean().

Using ob_end_clean(), there is a notice: "ob_end_clean(): failed to discard buffer of default output handler (1)".

Using ob_get_clean(), there is even a double notice: "ob_get_clean(): failed to delete buffer of default output handler (1)".

I understand, that only cleanable buffer can't be flush and delete. So why in manual these functions are under control PHP_OUTPUT_HANDLER_CLEANABLE const? I'm confused.

Test script:
---------------
ob_start(null, 0, PHP_OUTPUT_HANDLER_CLEANABLE);    
ob_end_clean();
    
ob_start(null, 0, PHP_OUTPUT_HANDLER_CLEANABLE);    
ob_get_clean();



Expected result:
----------------
No notice, and no buffer after function invocation.

Actual result:
--------------
ob_end_clean() produces notice:
Notice: ob_end_clean(): failed to discard buffer of default output handler (1) 

ob_get_clean() produces double notice:
Notice: ob_get_clean(): failed to discard buffer of default output handler (2)
Notice: ob_get_clean(): failed to discard buffer of default output handler (2)