1, flush(), example:
for( $i = 0; $i < 3; $i++ ) { print("OK<BR"); flush(); sleep(1); }
2, ob_start, bool ob_start ( [callback output_callback])
callback function will be called when ob_end_flush() is called.
3,bool ob_end_flush ( void )
4, ob_get_flush will return the buffer as string
5, ob_get_length will return the size of the buffer.
6, ob_clearn
7, ob_end_clean
8, ob_flush()