Description:
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The docs page for ob_get_clean() (http://php.net/manual/en/function.ob-get-clean.php) does not mention the PHP_OUTPUT_HANDLER_REMOVABLE flag even though it is required since it removes the buffer (ob_end_clean() specifies it correctly).

Test script:
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// Skipping the PHP_OUTPUT_HANDLER_REMOVABLE flag:
ob_start( null, 0, PHP_OUTPUT_HANDLER_CLEANABLE | PHP_OUTPUT_HANDLER_FLUSHABLE );
ob_get_clean();
// Fails with: Notice: ob_get_clean(): failed to discard buffer of default output handler (1)