Tag Archives: Technology/Internet

Zend Framework: Simple Acl Front Controller Plugin

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access with Zend_Acl

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:

<?php
 
class AclInit extends Zend_Controller_Plugin_Abstract
{
    public function preDispatch(Zend_Controller_Request_Abstract $request)
    {
        // create new acl object
        $acl = new Zend_Acl();
 
        // define resources. typically there are
        // only four resources from the CRUD functionality
        // but there can be added more resources
        $acl->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');
        }
    }
}

Friday Algorithms: JavaScript Merge Sort

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Merge Sort

This week I’m going to cover one very popular sorting algorithm – the merge sort. It’s very intuitive and simple as it’s described in Wikipedia:

  • If the list is of length 0 or 1, then it is already sorted. Otherwise:
  • Divide the unsorted list into two sublists of about half the size.
  • Sort each sublist recursively by re-applying merge sort.
  • Merge the two sublists back into one sorted list.

Here’s the Source

(JavaScript)

var a = [34, 203, 3, 746, 200, 984, 198, 764, 9];
 
function mergeSort(arr)
{
    if (arr.length < 2)
        return arr;
 
    var middle = parseInt(arr.length / 2);
    var left   = arr.slice(0, middle);
    var right  = arr.slice(middle, arr.length);
 
    return merge(mergeSort(left), mergeSort(right));
}
 
function merge(left, right)
{
    var result = [];
 
    while (left.length && right.length) {
        if (left[0] <= right[0]) {
            result.push(left.shift());
        } else {
            result.push(right.shift());
        }
    }
 
    while (left.length)
        result.push(left.shift());
 
    while (right.length)
        result.push(right.shift());
 
    return result;
}
 
console.log(mergeSort(a));

It’s interesting to see what happens in the Firebug’s console:

[34, 203, 3, 746] [200, 984, 198, 764, 9]
 
[34, 203] [3, 746]
 
[34] [203]
 
[3] [746]
 
[200, 984] [198, 764, 9]
 
[200] [984]
 
[198] [764, 9]
 
[764] [9]
 
[3, 9, 34, 198, 200, 203, 746, 764, 984]

Actually the tricky part in this algorithm is the merge function – it does all the work.

HTML5 geolocation – What If the User Doesn’t Share His Position?

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HTML5 Geolocation

So far we were used to expect something like this from our mobile phones with built-in GPS support. Every image or video clip then was automatically “tagged” with latitude & longitude geo data. With HTML5 coming features we discover new cool things we can do with our browsers. Such cool thing is the geolocation.

Geo Location

Support

As you may guess not every browser is supporting these HTML5 features, but out in the web there is quite good collection of tables comparing different browsers and their support level.

Firefox

This – as expected is a browser that supports this geo tagging. First of all you’ve to allow your browser to use your geo coordinates, as this can be private information.

Browser GEO Location

Once you do it you can access the geo coordinates, which by the way are quite accurate, with JavaScript.

What if you don’t share your position?

What happens if you don’t want to share your position? Actually I ran in this situation and as my application waited the coordinates – it was completely blocked.

The examples doesn’t show you something special. They simply describe how to get the coordinates, but doesn’t tell you what if the user doesn’t click on the “share” button.

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(getPos);
}
...
 
function getPos(position) 
{
    position.coords.latitude;
    position.coords.longitude;
}

Of course getPos() can be simply an anonymous function:

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(function(position) {
            position.coords.latitude;
            position.coords.longitude;
        });
}

Only the Firefox documentation tells you how to handle errors, simply add one more parameter – callback, for getCurrentPosition() method:

if (!!navigator.geolocation) {
        navigator.geolocation.getCurrentPosition(getPos, onError);
}
...
 
function getPos(position) 
{
    position.coords.latitude;
    position.coords.longitude;
}
 
function onError()
{
   // handle error
}

Now you know where you don’t want to be.

Map Marker

Send Authenticated POST Request with Zend_Http_Client

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There is an easy way to send requests with Zend_Http_Client either in GET and POST. Actually you can request not only with GET and POST methods, but with any other http request method.

$httpClient = new Zend_Http_Client('http://....');
// request via post
$response = $httpClient->request(Zend_Http_Client::POST);
// or get
$response = $httpClient->request(Zend_Http_Client::GET);

However the interesting and useful thing is that you can perform authenticated requests:

$httpClient = new Zend_Http_Client('http://username:password@example.com');
// or define it later
$httpClient = new Zend_Http_Client('http://example.com');
$httpClient->setAuth('username', 'password');

That’s an opportunity to send/receive authenticated POST requests.

$httpClient = new Zend_Http_Client('http://username:password@example.com');
// now post
$httpClient->request(Zend_Http_Client::POST);

Use Zend_Translate to Translate Your Web App

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There are some really good reasons to use Zend_Translate for your multilingual site instead of some other technique. Actually you can definitely simulate something like this Zend component with and array or ini file, but here are some good things to mention.

1. Write a human readable source file

In fact you can do this even without Zend_Translate. Image you’ve an ini file with some pairs like:

lblMyLabel = "My Label"

Nobody says this cannot be “more” human readable – like so:

My Label = "My Label"

Than you can support several files i.e. en.ini, de.ini, etc. where you can translate this label. The problem is that once you read the ini file you’ve to deal with those white spaces into the labels, while with Zend_Translate you can simply call them with:

$translate->_("My Label");

2. Default values for missing labels

Zend_Translate forces you to define a source file. Which is really great, because you always have a default value. Assuming that you don’t have a specific label translated in one of the ini files, you’ll get the default value from the source file, and defining source and other files is as easy as:

// en.ini
My Label = "My Label"
 
// de.ini
...
 
// while the locale is de_DE you'll have 
// the default value returned
$translate->_("My Label"); // will return My Label from the en.ini

3. Locales

It’s really great that you can directly setup a locale for this module. Thus you have more flexibility when switching between languages and you can benefit from the power of the framework when reading some browser specific locales. Here’s some code:

$translate = new Zend_Translate('ini', 'en.ini', 'en');
$translate->addTranslation('de.ini', 'de');
 
// than when you setup the translation locale
$translate->setLocale('en');

4. Cache

One of the greatest things about Zend_Translate is the native support of cache. It’s so cool! Actually the labels of a large web system are pretty static and don’t change every day. In other hand in large scale systems there are lots of labels, and the load time will be faster with cache.

$frontendOptions = array('lifetime' => 600, 'automatic_serialization' => true);
$backendOptions  = array('cache_dir' => 'path_to_cache_dir');
 
$cache = Zend_Cache::factory('Core', 'File', $frontendOptions, $backendOptions);
 
Zend_Translate::setCache($cache);

It’s a great advantage to use Zend_Translate after all this. Actually I have finished projects without any use of it, but I really can’t imagine how I’ll work now without it!