Web application frameworks – stoimen's web log

How to Overcome Zend_Cache_Frontend_Page’s Problem with Cookies

Stoimen — Wed, 03 Nov 2010 14:19:25 +0000

Zend_Cache_Frontend_Page

First of all there are several things to know about Zend Framework and caching. Whenever you work on a big web application caching is one of the mostly used mechanisms of speeding up the app and improve user performance. In general the task and the solution are pretty simple and natural.

As the application grows up the visitors become more and more impatient about what they receive. A single page is becoming slower and slower and the result is painful. First of all every time a user hits a page the application server uses the web server, a script interpreter, a database server and potentially the file system. But that’s not all. After all this output is generated on the server, as HTML in the most cases, it is sent to the client where again CSS and JavaScript engines parse and execute them.

In this scenario it’s easy to imagine how many time is spent. While there are several techniques to optimize the client side by optimizing JavaScript, CSS and the static images used for the design of the site, here I’m going to talk more about the backend.

Beside the Optimization

Let’s assume we’ve one of the very used combination between Apache (as a webserver), PHP (as server scripting language) and MySQL (as database server). Here you can choose to optimize all three of them. However beside the optimization of them one of the most simple steps you can do is to cache the output generated by these three branches of your web app.

Caching the Content

In fact you can cache only single parts of the whole process. For instance you can cache only the result returned by some slow database query. Let’s imagine a query takes about 2 seconds to execute. Now you can cache the result into a file and during the cache is active, i.e. it has not expired, the application takes it from a file stored somewhere in the file system.

In a typical Zend Framework scenario you can first setup the frontend and backend options of the cache.

$frontendOptions = array(
	'lifetime'                => 600, // in seconds - this is 10 seconds
	'automatic_serialization' => true,
);
$backendOptions = array('cache_dir' => 'cache/');
$cache = Zend_Cache::factory('Core', 'File', $frontendOptions, $backendOptions);
		
$cacheKey = md5('mykey');

if (!$cache->load($cacheKey)) {
	$slowQueryResult = $article->fetchAll();
	$cache->save($slowQueryResult, $cacheKey);
} else {
	$slowQueryResult = $cache->load($cacheKey);
}

You can setup different options here by setting up the cache directory, lifetime, etc.

Note that the cache directory must exists and with write permissions and Zend Framework doesn’t create it for you and will throw error.

The problem here is that now you cache only part of the generated content and in many cases this is still too slow for most of the users. However all the work (in most of the cases) of the web server, the script interpreter and the database server result in a simple HTML output. What if you have this output generated or cached for you and when the user hit the page the server will return this pre-generated code?

This is indeed very fast, because it’s similar to return a text file, as the HTML is simply formatted text.

Caching the Entire Page

Before I proceed, I’d like to say that I work with Zend Framework 1.9.x. Now in the latest versions of ZF there are new mechanisms of caching the output even Zend_Cache_Frontend_Page works fine on them.

You can simply setup the page cache within few simple lines of code:

$fo = array(
    'lifetime' => 600,
    'regexps' => array(
        '^/' => array(
	'cache' => true,
         'cache_with_cookie_variables' => true,
        ),
    )
);

$bo = array(
    'cache_dir' => 'cache/'
);

$cache = Zend_Cache::factory('Page', 'File', $fo, $bo);
$cache->start();

However my advise is to place this code as high as possible, because this will cache everything generated as output. It’s a good practice if you place this even in the bootstrap before you make the connection with the database. Actually you don’t need a database connection when you’ve to return a simple text(html) file.

This will improve your app’s performance a lot!

However there are few things to know. When you setup the cache to work even with cookie variables, you can see that hitting the page with different browsers Zend Framework will generated different cache pages. This is quite useless because than you don’t have any benefit of caching the content.

First of all let me say that THIS IS NOT A BUG! of ZF. Simply the framework will use the cookie variables to generate the cache key. It’s obvious that different browsers, even more different users, will have different cookie set and the framework will generate different cache keys for them.

Thus you’ve to change the setting to generate the cache key from cookie variable by explicitly set this option to false:

$fo = array(
    'lifetime' => 600,
    'regexps' => array(
        '^/' => array(
		 'cache' => true,
         'cache_with_cookie_variables' => true,
         'make_id_with_cookie_variables' => false,
        ),
    )
);

$bo = array(
    'cache_dir' => 'cache/'
);

$cache = Zend_Cache::factory('Page', 'File', $fo, $bo);
$cache->start();

Note that in this example we cache every single page generated by the framework explained in the regexps. This is not so good especially when the users have the possibility to login and to see customized content for them, so you can be careful what you cache.

A typical problem that this solution solves is when your application uses Google Analytics. As you may know Google Analytics sets up a cookie every time when an user hits the page, so every time the framework will generate a different cache for him and in result he won’t see any benefit and performance improvement from your site.

Models in Zend Framework – Initialize All Methods with init()

Stoimen — Mon, 09 Aug 2010 19:05:05 +0000

In the Zend Framework’s documentation there are lots of examples how you can initialize all the actions in a given controller – by simply adding the init() public method in the controller’s code:


But did you know that you can do the same thing with any model in ZF? However you can setup a cache for every method or something else, but definitely it will execute for every method:

Of course that means that directly calling the readAll() function the init() method is called also - automatically.
Conclusion
There are good and bad parts about this. You'll have this code executed for every method and if you have twenty of them and the init() method is practically used for only a couple of the member functions - than this will be useless.

Related posts:

Setting Up Zend Framework with Modules 
Bind Zend Action with Non-Default View – Part 2 
Default Error Handling in Zend Framework 
Zend Framework: Simple Acl Front Controller Plugin

Zend_Validate_Db_RecordExists in Zend Framework 1.10+

Stoimen — Thu, 22 Jul 2010 11:24:46 +0000

Zend_Validate_Db_RecodExists is an extremely useful validator in Zend Framework when you’d like to be sure that a give row exists. Now it seems to be even better. Before you could check for a specific row by only comparing a value to the specified column:

$validator = new Zend_Validate_Db_RecordExists('db_table_name', 'column_name');
if ($validator->isValid(122)) {
   ...
}

which made it useless when you’d like to compare by more than one column. Now this is changed and you can even exclude given rows by adding an exclude clause.

$validator = new Zend_Validate_Db_NoRecordExists(
    array(
        'table' => 'users',
        'field' => 'username',
        'exclude' => array(
            'field' => 'id',
            'value' => $user_id
        )
    )
);

Media RSS and ZF – Part 2

Stoimen — Wed, 14 Jul 2010 19:05:15 +0000

Here’s the promised chunk of code making the most simple bridge between Zend Framework and Media RSS.

Step 1

Just add a simple action in a controller:

class IndexController extends Zend_Controller_Action
{
	public function indexAction()
	{
	    $this->getResponse()->setHeader('Content-Type', 'application/xml');
	    $this->view->somevar = 'some value';
	
	    echo $this->view->render('index/index.xml');
	
	    $this->_helper->layout()->disableLayout();
	    $this->_helper->viewRenderer->setNoRender(true);
	}
}

Step 2

After you’ve setup the xml file as a view script – you can simply access it as a normal Zend Framework view:


  
   <?php echo $this->somevar ?>
   ...
   other media rss elements
   ...

Zend Framework: Simple Acl Front Controller Plugin

Stoimen — Tue, 06 Jul 2010 19:00:59 +0000

Almost every web site need some abstraction over the access control list (ACL) to grant access of its users. As usual Zend Framework has quite good mechanism to deal with this – Zend_Acl.

Out in the web there are a lot of resources about Zend_Acl’s usage, so I ain’t going to cover it one more time, but simply copy/paste a very small front controller plugin implementing the basic usage of Zend_Acl.

Note that instead of defining the __construct() here is called preDispatch where the request is passed as a parameter. However only by copy pasting not every answer will be given. That’s why I’m going to write more about Zend_Acl in my future posts, for now only the source code:

add(new Zend_Acl_Resource('index'))
            ->add(new Zend_Acl_Resource('create'))
            ->add(new Zend_Acl_Resource('read'))
            ->add(new Zend_Acl_Resource('update'))
            ->add(new Zend_Acl_Resource('delete'));

        // define roles
        $acl->addRole(new Zend_Acl_Role('guest'))
            ->addRole(new Zend_Acl_Role('admin'));

        // define privileges
        $acl->allow('guest', array('index', 'read'))
            ->allow('admin');

        // setup acl in the registry for more
        Zend_Registry::set('acl', $acl);

        // check permissions
        if (!$acl->isAllowed('guest', $request->getActionName())) {
            $request->setControllerName('error');
            $request->setActionName('error');
        }
    }
}

Bind Zend Action with Non-Default View – Part 2

Stoimen — Wed, 23 Jun 2010 14:26:41 +0000

Typical Setup

Typically Zend Framework is setup to bind every controller’s action to a specific view. The names of the action and the view script must be the same, or at least must be similar – following the ZF’s convention.

Thus if you name an action, let’s say, indexAction(), you’ve to create an index.phtml file into the views/scripts/index/ folder. Let me remind you that this is what is called a typical setup, but this may vary from one installation to another.

Thus everything’s fine and the MVC does its best. After the user requests a specific uri, the framework parses it and finds the controller, than the action and than the view script – and there is a view script for every single action.

When there are two or more actions – there are two or more .phtml (view scripts) files.

Some Exceptions

Sometimes you have very similar logic, but very different markup between two actions. As the logic goes to the controller/action and the markup into the view, the question is can you simply have one action in the controller, but with two different .phtml file as a view scripts? Of course switching between those two (or more) with some conditionals.

Solution No. 1

However once I posted a simple, and working, solution. There you have again two actions and two scripts:

view->title = "My Title";
		
		// if the logic requires a different markup
		// simply redirect to another view
		if (some_expression) {
			$this->_forward('second');	
		}	
	}
	
	public function secondAction()
	{}
}

// in the application/views/scripts/index
// 1. first.phtml
title ?>

// 2. second.phtml
title ?>

As you can see in the second action there’s no logic – it’s only serving the role of a bridge between the views. Everything is setup into the first action, but the second action is doing the relation with the second.phtml view script.

Solution No. 2

However there’s another solution with only one action and two scripts which makes something like that shown on the diagram bellow:

The only thing to do is to add some code to your action:

view->title = "My Title";
		
		// if the logic requires a different markup
		// simply redirect to another view
		if (some_expression) {
			echo $this->view->render('index/second.phtml');
			$this->_helper->viewRenderer->setNoRender(true);
		}	
	}
}

// in the application/views/scripts/index
// 1. first.phtml
title ?>

// 2. second.phtml
title ?>

Note that you’ve to setNoRender on the view renderer once you render the other script!

Redirect with Zend Framework

Stoimen — Mon, 21 Jun 2010 14:31:10 +0000

Once I wrote about redirecting with Zend Framework, but what I missed back than was a common mistake. Although the code from my post is working, to be completely correct after redirecting I’d to add an exit() statement.

This is important because the header is changed and if something goes after the redirect there will be some problems. Finally the correct snippet is:

public function() {
	$this->_redirect('some_url');
	exit();	
}

JSON and Zend Framework? – Zend_Json

Stoimen — Thu, 10 Jun 2010 14:08:59 +0000

That’s really a good Zend Framework’s class that help you do the encode/decode job very easily. First of all it escapes everything for you and second it prints a correct/valid code. Note that sometimes if you have a trailing whitespace after the closing PHP tag – ?> that will result in an error.

Here’s some code:

public function jsonAction()
{
	$data = array(3,4,'test', 'my-name' => 3,4);

	echo Zend_Json::encode($data);

	$this->_helper->viewRenderer->setNoRender(true);
	$this->view->layout()->disableLayout();
}

and the result is:

{"0":3,"1":4,"2":"test","my-name":3,"3":4}

Note that all integers are printed without double quotes – which saves some space!

Download Files with Zend Framework

Stoimen — Tue, 25 May 2010 14:06:13 +0000

Download a File

The title may sound unclear enough, but the task is simple. You’ve to make a file download process within a Zend Framework’s controller. Let’s assume we’ve the DownloadController setup:


In PHP there are at least three simple lines of code that will do the job of downloading a file.
header('Content-Type: image/jpeg');
header('Content-Disposition: attachment; filename="logo.jpg"');
readfile('images/logo.jpg');

Note that here there is a content-type header, which is important cause the browsers understands what kind of file is supposed to be downloaded. The second line suggests a name of the downloaded file and the third one returns the file to the client.
Download a File ... within Zend Framework
Those three lines wont work alone in a ZF application, because there's no view, but even if you create a .phtml (view) file for this action it won't work, because the header of the returned file is modified.
The question is how to possibly return the file for download, perhaps write some statistics to the database and if there's a problem (some permission issues for instance) return a message to the user.
The Basic Solution
The solution is simple. First make it work by disabling the view and possibly the layout for this action:
public function indexAction()
{
	header('Content-Type: image/jpeg');
	header('Content-Disposition: attachment; filename="logo.jpg"');
	readfile('images/logo.jpg');
	
	// disable the view ... and perhaps the layout
	$this->view->layout()->disableLayout();
        $this->_helper->viewRenderer->setNoRender(true);
}

Than add some code where you can check the permissions. Just because there's no view for this action you can redirect to another - errorAction():
public function indexAction()
{
    if (userHasNoPermissions) {
        $this->view->msg = 'This file cannot be downloaded!';
        $this->_forward('error', 'download');
    }

    header('Content-Type: image/jpeg');
    header('Content-Disposition: attachment; filename="logo.jpg"');
    readfile('images/logo.jpg');

    // disable layout and view
    $this->view->layout()->disableLayout();
    $this->_helper->viewRenderer->setNoRender(true);
}

But that still will prompt you a file to download, so there should be a return statement that will return false:
public function indexAction()
{
    if (userHasNoPermissions) {
        $this->view->msg = 'This file cannot be downloaded!';
        $this->_forward('error', 'download');
        return FALSE;
    }

    header('Content-Type: image/jpeg');
    header('Content-Disposition: attachment; filename="logo.jpg"');
    readfile('images/logo.jpg');

    // disable layout and view
    $this->view->layout()->disableLayout();
    $this->_helper->viewRenderer->setNoRender(true);
}

So here's the complete source of DownloadController.php:
view->msg = 'This file cannot be downloaded!';
	        $this->_forward('error', 'download');
	        return FALSE;
	    }
	
	    header('Content-Type: image/jpeg');
	    header('Content-Disposition: attachment; filename="logo.jpg"');
	    readfile('images/logo.jpg');
	
	    // disable layout and view
	    $this->view->layout()->disableLayout();
	    $this->_helper->viewRenderer->setNoRender(true);
	}	
	
	public function errorAction()
	{}
}

and the error.phtml:
msg ?>


Related posts:

Setting Up Global Cache in Zend Framework 
Models in Zend Framework – Initialize All Methods with init() 
Upload a File with Zend Framework 
Download Images with PHP

Check YouTube Video Existence with Zend_Gdata_YouTube

Stoimen — Fri, 21 May 2010 07:43:57 +0000

The Video Has Been Removed?!

Have you ever seen the famous message on YouTube: “This video has been removed by the user.”, but what if you’re trying to grab that video via the Zend_Gdata_YouTube?

That can happen when you’re reading the feed for a channel or a user’s list of videos. In the feed everything’s OK – once the video is uploaded it appears into the feed. After that the user removes the video and visiting the link from the feed you’ll get the message above.

Actually what happens when you try to read this “video entry” within a Zend Framework’s application. There must be some way to catch this message?

Trying to Catch

The answer is pretty simple! Zend_Gdata_YouTube’s throwing an exception and it can be easily cached. Here’s some source code:

$apiKey = 'your_api_key';
$client = new Zend_Http_Client();
$gdata = new Zend_Gdata_YouTube($client, 'my-app', null, $apiKey);
try {
       $gdata->getVideoEntry($video_id);
} catch(Zend_Gdata_App_Exception $e) {
       echo $e->getMessage();
}