Re: Re: new data detect

From: "Sommai Fongnamthip" <sommai@thaithanakit.co.th> To: "Hugh Bothwell" <hugh_bothwell@hotmail.com>; <php-db@lists.php.net> Sent: Wednesday, July 25, 2001 10:37 PM Subject: Re: [PHP-DB] Re: new data detect > > At 22:28 25/7/2001 -0400, Hugh Bothwell wrote: > > >"Sommai Fongnamthip" <sommai@thaithanakit.co.th> wrote in message > > >>news:5.1.0.14.2.20010726085848.00a7f760@langsuan.thaithanakit.co.th... > > > Hi, > > > I decide to make real time application (like stock market or online > > > news). How could I know when new data arrive to table and retrieve them > >to > > > display or update in web page? > > > >You can't, actually, short of using server-side push; > > > >what you can do is periodically requery the server; either reload the page > >every so often, or (better) use a flag file - set it when data is changed - > >and check it in the background with JavaScript, then reload the page only > >when it is set. > > Why PHP cannot do background check with the same of Java Script? Because: (a) JavaScript runs on the client, so it can periodically call the server; PHP runs on the server, has no way to contact the client (short of server-side push ie a continuous connection). (b) JavaScript can run continuously (by setting a timer); PHP only runs when called.