Description:
------------
On 5_2 and 5_3, there is an inconsistency between ob_flush() and ob_get_flush() when attempting to flush a buffer created with the flag $erase=false:
 - ob_get_flush() raises a notice and does NOT flush the buffer; 
 - ob_flush() DOES flush the buffer.
 
Note that on HEAD, both ob_get_flush() and ob_flush() raise a notice and do NOT flush the buffer.
I think the behaviour in HEAD is correct. Here's a simple patch for 5_3 that resolves the inconsistency and makes it behave more like HEAD:

Index: output.c
===================================================================
RCS file: /repository/php-src/main/output.c,v
retrieving revision 1.167.2.3.2.4.2.9
diff -u -w -p -r1.167.2.3.2.4.2.9 output.c
--- output.c    18 Aug 2008 07:46:31 -0000      1.167.2.3.2.4.2.9
+++ output.c    18 Dec 2008 11:30:01 -0000
@@ -774,6 +774,10 @@ PHP_FUNCTION(ob_flush)
                php_error_docref("ref.outcontrol" TSRMLS_CC, E_NOTICE, "failed to flush buffer. No buffer to flush.");
                RETURN_FALSE;
        }
+       if (OG(ob_nesting_level) && !OG(active_ob_buffer).status && !OG(active_ob_buffer).erase) {
+               php_error_docref("ref.outcontrol" TSRMLS_CC, E_NOTICE, "failed to flush buffer %s", OG(active_ob_buffer).handler_name);
+               RETURN_FALSE;
+       }

        php_end_ob_buffer(1, 1 TSRMLS_CC);
        RETURN_TRUE;




More generally, the behaviour of output buffering functions when dealing with unerasable buffers could benefit from better docs. I will raise a separate doc bug with some suggestions.

Reproduce code:
---------------
<?php
function callback($string) {
	static $callback_invocations;
	$callback_invocations++;
	return "[callback:$callback_invocations]$string\n";
}

ob_start('callback', 0, false);

echo "Attempt to flush unerasable buffer - should fail... ";
var_dump(ob_flush());
// Check content of buffer after flush - if flush failed it should still contain the string above.
var_dump(ob_get_contents());
?>

Expected result:
----------------
[callback:1]Attempt to flush unerasable buffer - should fail...
Notice: ob_flush(): failed to flush buffer callback in %s on line 11
bool(false)
string(%d) "Attempt to flush unerasable buffer - should fail...
Notice: ob_flush(): failed to flush buffer callback in %s on line 11
bool(false)
"


Actual result:
--------------
[callback:1]Attempt to flush unerasable buffer - should fail... 
[callback:2]bool(true)
string(11) "bool(true)
"