PHP and Dynamic Meta Refresh

msmith-aust

Hi all,

I have a php script that builds a dynamic page from a mysql database. At the top of the page I have a Meta Refresh set to 30 secs so the page is always up to date.

What I'd like to do is make the refresh dynamic. Basically if nothing has changed then no need to reload. Since every reload does a db query even if it is not needed.

Is there any way to set up a trigger of some sort so that it only refreshes when a new INSERT or UPDATE is done to the database?

Any info would be GREATLY appreciated 🙂

Mike

jariizumi

A PHP page is static once it's been sent to the client. Unless you're talking about persistent connections and inconspicuously adding little JavaScript window.location's at the bottom (although how would you know when a query has been executed but by running queries every second?), I can't think up of a way to modify a page after it has been sent.

msmith-aust

Well....After a bit of thought I began trying a couple things. Please let me know if anyone see's a problem with this.

Any time I do an update or insert, I write a GMT timestamp to a file(output.txt).

I broke the page into 2 frames(top - 1%, main - 99%). The top frame is where I put the Meta-Refresh for every 30 secs. I have it check the timestamp in in output.txt against a timestamp of the initial load of top.php.

-= top.php =-

<META HTTP-EQUIV="REFRESH" CONTENT="30">
<?
$timestamp=(gmmktime(gmdate("Y-m-d H:i:s"))-30);
$output = file("output.txt");
if ($output[0] >= $timestamp)
echo "<body bgcolor=\"#F5F5F5\" onload=\"parent.main.location.href='main.php'\">\n";
else
echo "<body bgcolor=\"#F5F5F5\">\n";
?>
</body>

I figured it would be better to reload this top frame every 30 secs since it's size is so small(90b) and it save me from doing needless db queries. The main.php page is running about(7k-12k) depending on the number of events.

Comments are welcome...It seems to work. At least from the initial test I did.