Description:
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It is possible to create an unerasable output buffer by setting the flag $erase=false when calling ob_start().

This flag is documented, but its impact on other output buffering functions is not very clear.

I propose adding a sentence to the doc of each of the affected functions as follows:

ob_clean():
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not cleaned.


ob_end_clean():
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not cleaned and is not destroyed.


ob_end_flush():
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not flushed and is not destroyed.


ob_get_clean():
PHP5:
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not cleaned.
PHP6:
If the buffer is unerasable, the contents of the buffer is returned, but a notice is raised and the buffer is not cleaned.


ob_get_flush():
PHP5:
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not flushed.
PHP6:
If the buffer is unerasable, the contents of the buffer is returned, but a notice is raised and the buffer is not flushed.


And the following will be true once bug 46897 is fixed (currently, the behaviour is inconsistent):
ob_flush():
If the buffer is unerasable, a notice is raised and the function returns false; the buffer is not flushed.


Reproduce code:
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n/a

Expected result:
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n/a

Actual result:
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n/a