Plug-in PHP: 100 Power Solutions in Java

Drawer Code 128 Code Set A in Java Plug-in PHP: 100 Power Solutions

make cups of coffee or do the shopping or even when they go to bed Unfortunately, leaving a program running in such cases can very soon tie up even a powerful server One solution to this is to use an Ajax call to fetch all new posts instead of retaining an open connection to the server, This way the server would only be polled every now and then But the solution I have used here, as you ll see in the following section, is to exit from displaying the chat after a given length of time and then ask the user to click a link to reload the chat it s a really simple way of ensuring the user is still active

Using this plug-in can be as simple as the following code, which restarts the script when the user clicks a link:

if (!PIPHP_ViewChat('chatroomtxt', 'fredsmith', 300)) echo "Error Could not open the chat data file"; else echo "<a href='" $_SERVER['PHP_SELF'] "'>Click here to continue</a>";

It requires just three arguments: the name of the chatroom datafile; the username of the person viewing the chat; and the timeout in seconds of the program By using the PHP variable $_SERVER['PHP_SELF'], it doesn t matter what your program is called because this variable will refer to it correctly If you know that the current user is still active for example, because they have recently posted a message you could restart the script automatically for them In this case, you needn t impose a Click here message on them One way to do this would be to load in the $datafile file and process it looking for any From fields with the user s username If you find one, then the user posted recently and you could auto renew the chat using a bit of JavaScript, like this:

die("<script>selflocation='" $_SERVER['PHP_SELF'] "'</script>");

The die() function acts as a combined echo and exit statement and the JavaScript in it will cause the current page to be reloaded Of course, when you run your own chat server you ll soon see the kinds of loads it is under and the amount of time you can afford to leave the plug-in running in order to get the best uninterrupted user experience For example, you may find that 15 minutes is more appropriate, particularly when fewer users are active The main thing, though, is that you can quickly and easily offer a fast and flexible chat service with a few lines of PHP code, without having to install large programs, or rely on Java or Flash programs, and you don t need to be stuck with a look and feel someone else has designed The fact that this chat is only a few lines of code means you can tailor it exactly to your requirements, without delving through hundreds or thousands of lines of code

retrieve data to and from the server) is an even better solution to providing a smooth and flexible chat service, and you wouldn t need to change a lot to implement it However, it can be tricky to get just right and would be too large a project for this book That said, in 11 I do show you the principles of making Ajax calls and provide you with the plug-ins you will need

8:

function PIPHP_ViewChat($datafile, $username, $maxtime) { if (!file_exists($datafile)) return FALSE; set_time_limit($maxtime + 5); $tn = time(); $tstart = "<table width='100%' border='0'><tr><td " "width='15%' align='right'>"; $tmiddle = "</td><td width='85%'>"; $tend = "</td></tr></table><script>scrollBy(0,1000);" "</script>\n"; $oldpnum = 0; while (1) { $lines = explode("\n", rtrim(file_get_contents($datafile))); foreach ($lines as $line) { $thisline = explode("|", $line); $postnum = $thisline[0]; $to = $thisline[1]; $from = $thisline[2]; $message = $thisline[3]; if ($postnum > $oldpnum) { if ($to == "") { echo $tstart "$from:" $tmiddle $message $tend; } elseif ($to == $username || $from == $username) { echo $tstart "$from:" $tmiddle "(PM to $to) <i>$message</i>" $tend; } $oldpnum = $postnum; ob_flush(); flush(); } } sleep(2); if ((time() - $tn) > $maxtime) return TRUE; } }