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Caching between pages via memcached
Web2 and caching example from a Well House Consultants training course
More on Web2 and caching [link]

This example is described in the following article(s):
   • memcached - overview, installation, example of use in PHP - [link]

If you're searching for a page where you can try this code, select here

This example references the following resources:
http://www.wellho.net/pix/$imgname
http://www.wellho.net/course/ptfull.html
http://www.wellho.net/mouth/1733_memcached.html
http://www.danga.com/memcached/

Source code: cademo.php Module: H307
<?php

# Record number to look up
$calledfor floor($_REQUEST[calledfor] + 0); // force numeric integer!
$calledfor or $calledfor rand(3006,3012); // Fallback value!

# The database accessor is used if we do NOT have data in cache
function dbfetch ($recno) {
        
$c mysql_connect("127.0.0.1","wellho","xxxxxxxx");
        
mysql_select_db("wellho",$c);
        
$qr mysql_query("select iid,filename,descriptor ".
                
"from im_library where iid = $recno",$c);
        
$row mysql_fetch_assoc($qr);
        
$value "$row[filename] $row[descriptor]";
        return (
$value);
}

$memcache = new Memcache;
if (
$memcache->connect('127.0.0.1'11211)) {
        
$q "connected (memcache daemon is running)";
        if (
$gotten $memcache->get("demo:$calledfor")) {
                
### Daemon running and provided data from cache
                
$say "key $calledfor retrieved from memcached";
        } else {
                
### Daemon running but it was NOT cached
                
$say "key $calledfor from database (was NOT cached)";
                
# Never mind - fetch it and store for next time!
                
$gotten dbfetch($calledfor);
                
$memcache->set("demo:$calledfor",$gotten);
        }
} else {
        
### No Daemon running - just fetch from database!
        
$q "failed (sorry - daemon is not running)";
        
$say "key $calledfor fetched from database";
        
$gotten .= dbfetch($calledfor);
        
# No point in trying to save it - cacher isn't running!
}

# Following code is common code whatever the source!
# and represents the application

$parts explode(" ",$gotten) ;
$imgname array_shift($parts);
$imgtag "<img src=http://www.wellho.net/pix/$imgname>";
$text htmlspecialchars(implode(" ",$parts));
?>
<html>
<head>
<style type="text/css">
<!--
h1 {
        font-family: Arial, Helvetica, sans-serif;
        font-size: 36px;
        font-weight: bold;
        color: #CC00CC;
}
.tabtext {
        font-family: Arial, Helvetica, sans-serif;
        font-size: 12px;
        color: #004400;
}
-->
</style>
<title>Memcache demonstration in PHP</title>
<head>
<body><center>
--- daemon connect status: <?= $q ?> ---<br>
--- <?= $say ?> ---<br>
--- value is: <?= $gotten ?> ---</center><hr>
<h1>Caching database queries in memory in PHP</h1>
<table class=tabtext><tr><td valign=top>
<?= $imgtag ?><br>
<b><?= $text ?></b>
</td><td valign=top>
If you have a busy server with repeated database queries,
you may wish to use the <b>memcached</b> daemon.  This
service allows you to store a query's results in memory
(and even to share the cache between computers) so that
you don't have to keep repeating SQL and disc accesses.
<br><br>
Memcached is used on many very busy sites - it's ideal
for blog articles (where the recent ones will be cached),
images, and so on.
<br><br>
This is a demonstration of memcached in use, via a PHP
web page.  It's provided by Well House Consultants who
cover such topics on their
<a href=http://www.wellho.net/course/ptfull.html>PHP
techniques workshop</a> or on private courses.
<br><br>
You are also very welcome to view the source code (link
below) and read a little more about it in our blog
<a href=http://www.wellho.net/mouth/1733_memcached.html>here</a>.
<br><br>
The home page of memcached is
<a href=http://www.danga.com/memcached/>here</a>.
</td></tr></table>

</body>
</html>

Learn about this subject
This module and example are covered on our public PHP Techniques course. If you have a group of three or more trainees who need to learn the subject, we can also arrange a private or on site course for you.

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Other Examples
This example comes from our "Web2 and caching" training module. You'll find a description of the topic and some other closely related examples on the "Web2 and caching" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre or under an Open Training Notes License from our sister site http://www.training-notes.co.uk.

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This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

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Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

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