php判断客户端浏览器是否已经断开连接

<?php
date_default_timezone_set('asia/shanghai');
$starttime=date('h:i:s');
set_time_limit(30);
echo'ignore_user_abort:'.ignore_user_abort().'<br>';
ignore_user_abort(true);
echo'ignore_user_abort:'.ignore_user_abort().'<br>';
$i=1;
while(1){
if(!connection_aborted()){
echo"hello!!!--$i<br>";
ob_flush();
flush();
sleep(1);
$i++;
}else{
$endtime=date('h:i:s');
$status='seconds:'."$i connectionstatus:".connection_status()." connection_aborted:".connection_aborted();
file_put_contents('stop.txt',"$starttime->$endtime:stop $status");
exit();
}
}
?>