How to flush data to browser but continue executing in PHP

ob_start();

/*
 * Generate your output here
 */ 

// Ignore connection-closing by the client/user
ignore_user_abort(true);

// Set your timelimit to a length long enough for your script to run, 
// but not so long it will bog down your server in case multiple versions run 
// or this script get's in an endless loop.
if ( 
     !ini_get('safe_mode') 
     && strpos(ini_get('disable_functions'), 'set_time_limit') === FALSE 
){
    set_time_limit(60);
}

// Get your output and send it to the client
$content = ob_get_contents();         // Get the content of the output buffer
ob_end_clean();                      // Close current output buffer
$len = strlen($content);             // Get the length
header('Connection: close');         // Tell the client to close connection
header("Content-Length: $len");     // Close connection after $len characters
echo $content;                       // Output content
flush();                             // Force php-output-cache to flush to browser.
                                     // See caveats below.

// Optional: kill all other output buffering
while (ob_get_level() > 0) {
    ob_end_clean();
}