PHP’s recommended configuration is to run under Apache using the pre-fork multi-processing module (MPM).  The advantage to this is that Apache does not have to spin off another process to handle each request; it handles it in the same thread.  However, this means that each instance of the server must have all enabled modules loaded.  This means that each instance of the server (AKA “thread”) is very large, so the number of threads run is lower (typically 5-15 in a server the size we’re on).  Also, this means that each thread can only handle one request at a time; if you have 7 threads configured, each serving one of 7 requests, and an 8th request comes it, it has to wait for one to finish.  If the requests are served quickly, this may not be a problem; however, the avalanche of request that follow the typical front-page mention on mega-blogs can easily overwhelm it.

To fix this problem, there is another MPM, this one called worker.  In this scenario, there are spare thread waiting to fill requests, and these can spawn other threads to do further work if required.  So, the Apache threads would realize that a request needs to be handled by PHP, and pass it off to that process to be completed.  The Apache memory footprint is much smaller; it serves the images, scripts, and other static files, and passes off the requests that require heavy lifting.  PHP, then, has a (FastCGI) process where it receives these requests, processes them, and returns the response to the caller.  Because each of these threads only has to load the PHP requirements, they are smaller too, so you can have more threads processing at the same time; you just might survive that front-page mention!  (This is the same technique applied by LightTPD and Nginx, two other servers I tried at various times.)

It is in this scenario where PHP fails to live up to its expectations.  These PHP processes would simply stop responding, but the controller thinks they’re still there.  The end result to the user is a site that just sits and waits for output that will never come.  Eventually, they may receive a Gateway Timeout or Bad Gateway error.  The problem is worse on slower sites, but even popular sites seemed to fall victim to this from time to time.  This was also a problem whether PHP controlled its threads, or Apache controlled them.

The one thing that really perturbs me is instability.  If something is broken, I can fix it; if it works, I can fix it ’til it’s broke.  :)  But something that works sometimes, and other times doesn’t, simply won’t fly.  I was able to introduce some stability by restarting the server 4 times a day, but that’s a band-aid, not a long term solution.  I was tired of fighting.

Bottom line: the configuration required for a stable server is in opposition to a lean-and-mean configuration.  So, I installed the required Apache modules, and will continue to run my PHP-serving server at a configuration twice as large as it needs to be.  I’ll eventually move the Mono (.NET) processes to another machine, where the fast configuration won’t stability problems.

But, PHP isn’t all.  While I would still heartily recommend BlogEngine.NET to someone who was going to serve the blog from a Windows machine, but I had some issues getting upgrades to go smoothly under Mono.  It also is optimized for fast serving, at the expense of RAM.  At this point, that’s not the tradeoff we need.

Finally, with this update, the blog has received its first new theme.  It’s a clean, clear theme that should serve the content well.  Plus, the social media icons up in the corner are just too cool, IMO.  I’ve also applied tags to all posts except the “My Linux Adventure” series, and this theme displays them.  (Comments are not here now, but will be migrated shortly.)

So, there you have it.  Enjoy!

Scenario – You have two parent tables, and a child table with a many-to-one relationship with both parent tables, used to map entries in the two parent tables to each other. For this example, we’ll use these three tables…

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CREATE TABLE volunteer (
    vol_id  INTEGER  NOT NULL,
    vol_last_name  VARCHAR(50)  NOT NULL,
    ...etc...
  PRIMARY KEY (vol_id)
);
 
CREATE TABLE r_volunteer_area (
    rva_id  INTEGER  NOT NULL,
    rva_description  VARCHAR(255)  NOT NULL,
  PRIMARY KEY (rva_id)
);
 
CREATE TABLE volunteer_area (
    va_volunteer_id  INTEGER  NOT NULL,
    va_area_id  INTEGER  NOT NULL,
  PRIMARY KEY (va_volunteer_id, va_area_id),
  FOREIGN KEY (va_volunteer_id) REFERENCES volunteer (vol_id),
  FOREIGN KEY (va_area_id) REFERENCES r_volunteer_area (rva_id)
);

Algorithm – The three-step algorithm is as follows…

1. Create a comma-delimited string of IDs for the child table.
2. Delete the IDs from the child table that are not in the list.
3. Insert the IDs into the child table that are not there already.

Implementation – In PHP, if you have an array, it’s easy to come up with comma-delimited list. To get an array of values back in a post, define your fields with “[]” after the name…

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<input type="checkbox" name="area[]" id="chkArea1" value="1" />
<label for="chkArea1">Do Something</label><br />
<input type="checkbox" name="area[]" id="chkArea7" value="7" />
<label for="chkArea7">Do Something Else</label>

Here’s the PHP code, using PHP Data Objects (PDO) as the database interface, behind a helper class that creates the statement, appends the parameters, and executes it. (The “quoting” escapes the statement to avoid potential SQL injection attacks – putting it in its own class would make the implementation here much cleaner.)

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/**
 * STEP 1
 *    Create a comma-delimited list of IDs.
 */
 
// Quote will return the string as '2,3,4' - since we're using this
// as an IN clause of integers, we'll strip the quotes off.
$sAreas = $pdo->quote(join(",", $_POST["area"]));
$sAreas = substr($sAreas, 1, strlen($sAreas) - 1);
 
// Quote the volunteer ID.
$iVol = $pdo->quote($_POST["vol"], PDO::PARAM_INT);
 
/**
 * STEP 2
 *    Delete the IDs that are no longer in the list.
 */
$dbService->executeCommand(
    "DELETE FROM volunteer_area
    WHERE   va_volunteer_id = ?
        AND va_area_id NOT IN ($sAreas)",
    array($iVol);
 
/**
 * STEP 3
 *    Insert the IDs that are not yet in the list.
 */
$dbService->executeCommand(
    "INSERT INTO volunteer_area
        SELECT $iVol, rva_id
        FROM r_volunteer_area
        WHERE   rva_id IN ($sAreas)
            AND rva_id NOT IN
            (SELECT va_area_id
 
            FROM volunteer_area
            WHERE va_volunteer_id = ?)",
    array($iVol));

Modification – Suppose that now you accepted comments along with each of the checkboxes, so a simple two-integer insert/delete is no longer sufficient. You would still only need to break step 3 into two steps.

1. Get a list of IDs to update.
2. For each ID in the posted list
   1. If the ID exists in the update list, update it.
   2. Otherwise, insert it.

The implementation would then be able to use this list to make the decision without hitting the database every time.

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// Assume this returns an associative array of IDs.
$aUpdates = $dbService->performSelect(
    "SELECT va_area_id
    FROM volunteer_area
    WHERE   va_volunteer_id = ?
        AND va_area_id IN ($sAreas)",
    array($iVol));
 
foreach($_POST["area"] as $iArea) {
    if (in_array($iArea, $aUpdates)) {
        // Update the table
        ...etc...
    }
    else {
        // Insert into the table
        ...etc...
    }
}

I think you’ll agree that this is much better than spinning through a loop, doing a count on each ID to see if it exists, then either doing an update or an insert based on the count. And, while the implementation here is PHP, it could easily be implemented in any language that supports arrays and database access.

I went digging around in the source code, and found the line that actually pulls the count from the database. Using this parameter, I was able to integrate a spam count into the sidebar that has a look consistent with the rest of the site.

Here’s the code that’s in use on the theme on this site.

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<li id="spamstats">
	<h2><?php _e('Akismet-Eaten Spam:'); ?></h2>
	<ul>
		<li><a href="http://akismet.com"><?php
			echo(number_format(get_option("akismet_spam_count"))); ?>
			and counting...</a></li>
	</ul>
</li>

Of course, line 5 is the important one – that’s how to get the number, formatted for whatever locale the server is set up for. (On my personal blog, the number is up over 1,400!)

To use it, you simply put a pre tag, followed by “lang=[language]“. It will also do line numbering. Of course, with a single “language” parameter, the embedded language will not be highlighted as well. In this case, the previous plug-in works better; although the syntax highlighting has to be done manually, it can handle multiple languages.

Here is what the example from the “Category DropDowns in WordPress” post looks like with lang=”php”…

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<?php
/**
 * This creates a list of category links that can be used with a category dropdown
 */
$aCategories = get_all_category_ids();
$iMaxCat = 0;
foreach($aCategories as $iThisCat) {
    if ($iMaxCat < $iThisCat) {
        $iMaxCat = $iThisCat;
    }
}
$iMaxCat++;
?><div style="text-align:center;">
    <form name="categoryform" action="" style="text-align:center;">
    <script type="text/javascript">
        var aLink = new Array(<?php echo($iMaxCat); ?>);
<?php
foreach($aCategories as $iThisCat) {
    echo("aLink[$iThisCat] = \"" . get_category_link($iThisCat) . "\";\n");
} ?>
        function goCat() {
            window.location =
                aLink[document.getElementById('cat')[document.getElementById('cat').selectedIndex].text;
        }
    </script>
    <?php wp_dropdown_categories('class=sidebardropdown&orderby=name&show_count=1&hierarchical=1'); ?>
    <br />
    <button class="sidebarbutton" type="button" style="margin-top:5px;" onclick="goCat();">View Category</button>
    </form>
</div>

And, here’s what it looks like with lang=”javascript”…

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<?php
/**
 * This creates a list of category links that can be used with a category dropdown
 */
$aCategories = get_all_category_ids();
$iMaxCat = 0;
foreach($aCategories as $iThisCat) {
    if ($iMaxCat < $iThisCat) {
        $iMaxCat = $iThisCat;
    }
}
$iMaxCat++;
?><div style="text-align:center;">
    <form name="categoryform" action="" style="text-align:center;">
    <script type="text/javascript">
        var aLink = new Array(<?php echo($iMaxCat); ?>);
<?php
foreach($aCategories as $iThisCat) {
    echo("aLink[$iThisCat] = \"" . get_category_link($iThisCat) . "\";\n");
} ?>
        function goCat() {
            window.location =
                aLink[document.getElementById('cat')[document.getElementById('cat').selectedIndex].text;
        }
    </script>
    <?php wp_dropdown_categories('class=sidebardropdown&orderby=name&show_count=1&hierarchical=1'); ?>
    <br />
    <button class="sidebarbutton" type="button" style="margin-top:5px;" onclick="goCat();">View Category</button>
    </form>
</div>

This is another option, and is probably what I’ll use for single-language posts, or posts where the embedded language may not be crucial.

Here’s the code…

Edit: Code has been moved to this post.

This works for both “pretty” and standard links, as it uses the template tag get_category_link to specify the link.

The wireless network card still wasn’t recognized (phooey). I did some more searching, armed with the knowledge that I have an adm8211 chipset. One of the first hits under Google’s Linux search for “adm8211″ pointed me to a project called NDISwrapper. This is a “wrapper” that uses the vendor’s Windows DLL file, and converts the hooks from Windows to Linux. Doing this, this driver can (in theory) support most any network card, especially those that aren’t in the Linux Hardware Compatibility List (HCL). I downloaded it, compiled it, and followed the directions to install my driver under it. I still wasn’t able to create a connection, but on a hunch, I restarted the computer. NDISwrapper is also a kernel module, and I know that often those are only read at startup. Once the computer was restarted, I was able to create a connection, and now my network card works! YEA!!! (And it was only one night’s worth of work – much better.)

Now that I have networking working under both operating systems, I plan to try to get four things working the same, whether I’m booted to WXP or Linux – E-mail (using Mozilla Thunderbird), PHP (using Apache on Linux, IIS on WXP), MySQL (using the exact same version on both), and a web server that uses the same html root directory (again, Apache on Linux, IIS on WXP). If I didn’t already have IIS up, running, and configured under WXP, I’d probably just do Apache on both, but this will be interesting – it should work, as I don’t have many creative permission rules.