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().'
';
ignore_user_abort(true);
echo 'ignore_user_abort:'.ignore_user_abort().'
';
$i=1;
while(1){
    if(!connection_aborted()){
        echo "hello!!!--$i
";
        ob_flush();
        flush();
        sleep(1);
        $i++;
    }else{
        $endtime = date('h:i:s');
        $status = 'seconds:'."$i\t connection status:".connection_status()."\t connection_aborted:".connection_aborted();
        file_put_contents('stop.txt',"$starttime -> $endtime : stop \r\n$status");
        exit();
    }
}
?>