PHP_OUTPUT_HANDLER_FLUSHABLE

PHP_OUTPUT_HANDLER_FLUSHABLE is one of the accepted parameters for ob_start parameter #3 (optionally as a bitmask).

PHP_OUTPUT_HANDLER_FLUSHABLE — Controls whether an output buffer created by ob_start can be flushed by ob_flush. This flag does not control the behaviour of ob_end_flush or ob_get_flush.

PHP_OUTPUT_HANDLER_FLUSHABLE = 32;