--TEST--
ob_start(): Ensure unerasable buffer cannot be flushed by ob_flush()
--FILE--
<?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());
?>
--EXPECTF--
[callback:1]Attempt to flush unerasable buffer - should fail...
Notice: ob_flush(): Failed to flush buffer of callback (0) in %s on line 11
bool(false)
string(%d) "Attempt to flush unerasable buffer - should fail...
Notice: ob_flush(): Failed to flush buffer of callback (0) in %s on line 11
bool(false)
"