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  connection status: " . connection_status () . "  connection_aborted: " . connection_aborted ();
         file_put_contents ( ' stop.txt ' , " $starttime -> $endtime : stop  $status " );
         exit ();
    }
}
?>