I can not get the connection_aborted() function to work properly,
without flushing the output buffer a couple of times first.

Snip 1. Reports the connection as aborted if you interrupt the page download with "stop". Behaves correctly.

<?
ignore_user_abort(1);

for($i=0; $i<7; $i++) {
  sleep(1);
  echo "$i<BR>";
  flush();
}


$fp = fopen("/tmp/conn.txt","a");
if(connection_aborted()) fputs($fp,"** the connection was aborted  **\n");
else fputs($fp,"** the connection was OK  **\n");
exit;

?>

Snip 2. Says that the connection is OK, even though I've hit the "stop" button on my browser.

<?
ignore_user_abort(1);

for($i=0; $i<7; $i++) {
  sleep(1);
  echo "$i<BR>";
  //  flush();
}


$fp = fopen("/tmp/conn.txt","a");
if(connection_aborted()) fputs($fp,"** the connection was aborted **\n");
else fputs($fp,"** the connection was OK  **\n");
exit;

?>