(PHP 4, PHP 5, PHP 7, PHP 8)
flush — Flush system output buffer
Flushes the system write buffers of PHP and the backend used by PHP (e.g.: CGI, a web server). In a command line environment flush() will attempt to flush the contents of the buffers only whereas in a web context headers and the contents of the buffers are flushed.
Note: flush() may not be able to override the buffering scheme of the web server and it has no effect on any client-side buffering in the browser.
Note: This function does not have any effect on user level output handlers such as those started by ob_start() or output_add_rewrite_var().
flush() can interfere with output handlers that set and send headers in a web context (e.g. ob_gzhandler()) by sending headers before these handlers can do so.
This function has no parameters.
No value is returned.