Claudiu Persoiu

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Archive for the ‘Magento’ tag

Passing Magento Developer Plus certification

with 3 comments

Over an year ago, I started working on the Magento platform. In last year’s spring, a colleague from Optaros took the Magento Developer Plus certification exam. Since then, I began to like the idea of taking the certification exam, more as a motivation to learn the ins and outs of Magento.

Few months ago I was enrolled into a company study group for the certification. This was the first time I was sponsored for a certification (yes, until now everything was with my money). Preparing in a study group was a whole different experience.

Those who have more experience in a field balance the situation for the others and can give better examples from their own experience. It’s easier to understand from concrete examples then to try to imagine the scenarios yourself.

The certification is available through Prometric. So when you decide that you’re ready you can go to the website to purchase the voucher and schedule the exam.

The price for a voucher is 260$, not exactly cheap, but if you get to convince your boss to pay, it probably won’t be so bad. 🙂

But let’s get to the more interesting subject, the preparation.

Materials
Magento is not doing very good on this subject, there are very few materials and they are not centralized.

My sources were:
Magento® Certified Developer Plus Exam Study Guide – it is compulsive to read the guide and try to find answers to all the questions in it;
Magento training – especially Fundamentals of Magento Development
– blogs – I don’t want to give any names, there are a lot of people that write about the problems that they encounter and blog about the exam.

Unfortunately there isn’t a way like for PHP, ZF and Symfony where you can find all you need in one place, basically it depends on your luck and searching skills, there isn’t an “official version”. Things become weird when you find different approaches that are version specific.

How did I prepare
I began with the video training. It’s not perfect by it’s very helpful. I think the problem with most certifications is that you don’t get to work with all the available modules, just like in PHP you don’t get to work that much with sockets and streams.

Even though you don’t get the code and sometimes it is hard to follow and transcribe the examples, I think that the video tutorials are one of the most important sources at the moment.

Secondly, with the Study Guide in my hand, I began to try to answer the questions from it. When I joined the Study Group, the work divided between all the members in the group. My advantage was that it was the second generation of the group and we could profit from the documentation already developed by the first group.

If you’re preparing by yourself, I think the most important thing is to start, that’s the hardest part. And if you don’t know where to start, Google search the Magento questions, there are already a lot of people that are posting the explanations.

Answers for the questions from the first chapters are the easiest to find. As the number of the chapter is getting bigger, the number of Google results decreases.

But after the first questions, you should understand what is all about and in theory you will no longer need the documentation.

Use Mage::log(Varien_Debug::backtrace(true, false)); for stack trace and xdebug (http://xdebug.org/) to see what’s going on behind the scene. With patience, all the questions find their answers.

Because it was a group, the study was easier for me, but even so, to be sure of the explanation I has to dive deep in the code.

The exam
Some of the questions are difficult, but there are also accessible ones. The questions in the exam are off all levels of difficulty.

For Plus, the exam takes 2h not 2.5h as it is specified in the guide.

If you opted for Plus, there are 11 questions from Enterprise and advanced difficulty questions, of which 7 correct ones are required to pass. Basically this is the difficulty difference. For this questions it matters how much Enterprise experience you have.

In the guide for each exam, the questions are broken in percentages for each chapter.

Because in the non Plus certification there are no Enterprise questions, you only have to answer the necessary percentage from the full exam in order to pass and it’s not required to have a certain percentage from a certain chapter.

Things that are done regularly are analyzed in detail, it is important to understand how each function that is approached in each chapter works and what is the purpose of all those tags in the xml files.

Usually there are things you work with, or at least with which there is a good probability you have been working from the modules listed in the guide.

Post exam
Before you leave the room you’ll know if you’ve passed or not. When you exit the room you’ll receive a printed paper with the correct number of questions from each section from the total number .

In case you haven’t been successful you’ll receive by mail from Magento a voucher with a discount for a future attempt. They state that you should study at least 3 more weeks before you try again. Anyway, after you’ve taken the exam you’ll have a better view over your overall knowledge for a future attempt.

After few days (3 in my case) you will be able to see your profile on the Magento website as a reference.

The diploma got to Romania in about a month, the delivery address is the one from the Magento website account.

Best of luck!

Written by Claudiu Persoiu

16 February 2013 at 8:23 PM

Posted in Magento,PHP

Tagged with , , ,

Overwriting and deactivating Observers in Magento

with 2 comments

Sometimes we need to overwrite an observer. The first way that usually comes in mind is overwriting the model. Usually is named Observer.php, because this is the “best practice”.

And NO, you don’t have to overwrite the model. Observer.php doesn’t extend anything anyway and usually contains all of the module’s observers, so you can’t overwrite the same observer in more than one module.

How it works?
In magento when a new observer is added, it must have an unique identifier. This identifier is the key!

Actually, there is another element: “area”. When Mage::dispatchEvent(…) is performed, events will be dispatched using “area” and “identifier”.

For example, the admin notification system, which is observing “controller_action_predispatch”, will run:

=> "global"(area)
=> "controller_action_predispatch"(event)
=> "adminnotification"(identifier)

then:

=> "adminhtml"(area)
=> "controller_action_predispatch"(event)
=> "adminnotification"(identifier)

If the event was in the frontend area, it would be: “global” then “frontend”.

Overwriting
Overwriting is in fact a observer defined in the same config area as the original event (global, frontend or adminhtml), attached to the same event and with the same identifier as the original observer (e.g. adminnotification).

Let’s say we have to overwrite “adminnotification”. This observer is in Mage/AdminNotification. The unique identifier is defined in etc/config.xml:

...
  <adminhtml>
...
    <events>
      <controller_action_predispatch>
        <observers>
          <adminnotification>
            <class>adminnotification/observer</class>
            <method>preDispatch</method>
          </adminnotification>
        </observers>
      </controller_action_predispatch>
    </events>
...
  </adminhtml>
...

From the example above we can see:
– area: adminhtml
– event: controller_action_predispatch
– identifier: adminnotification

The module activation file will be: app/etc/modules/CP_AdminNotification.xml

<?xml version="1.0"?>
<config>
  <modules>
    <CP_AdminNotification>
      <active>true</active>
      <codePool>local</codePool>
      <depends>
        <Mage_AdminNotification/>
      </depends>
    </CP_AdminNotification>
  </modules>
</config>

I’ve added dependencies because without the original module, this module will be useless.

There’s a “best practice” to name a module that is overwritten with the same name as the original module.

The configuration file for this module, will contain practically everything you’ll need for the overwriting: area, event and identifier. The file is located in app/code/local/CP/AdminNotification/etc/config.xml:

<?xml version="1.0"?>
<config>
  <modules>
    <CP_AdminNotification>
      <version>0.0.1</version>
    </CP_AdminNotification>
  </modules>
  <global>
    <models>
      <cp_adminnotification>
        <class>CP_AdminNotification_Model</class>
      </cp_adminnotification>
    </models>
  </global>
  <adminhtml>
    <events>
      <controller_action_predispatch>
        <observers>
          <adminnotification>
            <class>cp_adminnotification/observer</class>
            <method>overwrittenPreDispatch</method>
          </adminnotification>
        </observers>
      </controller_action_predispatch>
    </events>
  </adminhtml>
</config>

The observer should contain all the new logic. The file is in app/code/local/CP/AdminNotification/Model/Observer.php, just like you would probably expect from the structure above.

<?php

class CP_AdminNotification_Model_Observer {

  public function overwrittenPreDispatch(Varien_Event_Observer $observer) {
    // noua logica din observer
  }
}

Disabling
Disabling is preaty similar to overwriting, the difference is in the config and the fact that an observer file is not needed anymore, because there isn’t a new logic.

The new config.xml file is:

<?xml version="1.0"?>
<config>
...
  <adminhtml>
    <events>
      <controller_action_predispatch>
        <observers>
          <adminnotification>
            <type>disabled</type>
          </adminnotification>
        </observers>
      </controller_action_predispatch>
    </events>
  </adminhtml>
</config>

Written by Claudiu Persoiu

17 May 2012 at 9:59 PM

Posted in Magento,PHP

Tagged with ,

Magento – Create a custom shopping cart price rule

with 2 comments

This is not a tutorial about setting up a Shopping Cart Price Rule in Magento, but rather about implementing a new one.

A new type of rule in Magento needs a couple of things:
– modify the admin area to add the new rule using an observer for adminhtml_block_salesrule_actions_prepareform,
– a way to apply the new rule using an observer for salesrule_validator_process.

Let’s build an example. Let’s say there is a Shopping Cart Price Rule that offers different discounts according to the number of products in the cart. The value that’s going to be used for the discount increment ($step) will be calculated. The first product will not receive a discount, the second product will receive a discount of $step, the third product will have a discount of 2*$step, until the maximum discount value will be reached. The following products will have a maximum discount. Ex:
Discount Amount = 50
Discount Qty = 5
Step = Discount Amount / Discount Qty = 10

Discount outcome:
– 0% prod 1
– 10% prod 2

– 50% prod 6
– 50% prod 7

The first step is the module activation using the file: app/etc/modules/CP_ProductNrDiscount.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <CP_ProductNrDiscount>
            <active>true</active>
            <codePool>local</codePool>
        </CP_ProductNrDiscount>
    </modules>
</config>

The first observer, adminhtml_block_salesrule_actions_prepareform, must be in the “adminhtml” section of the config, because it will involve the admin. This observer will have access to the admin form, in order to modify it.

The second observer, salesrule_validator_process, can be in the “frontend” or “global” section of the config. If it’s in the frontend section, it will only apply to the frontend section. If it’s in the global section it will also apply to backend. Usually, global is necessary when there are actions on the cart in the backend.

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <CP_ProductNrDiscount>
            <version>0.0.1</version>
        </CP_ProductNrDiscount>
    </modules>
    <global>
        <models>
            <productnrdiscount>
                <class>CP_ProductNrDiscount_Model</class>
            </productnrdiscount>
        </models>
        <events>
            <salesrule_validator_process>
                <observers>
                    <productnrdiscount>
                        <type>model</type>
                        <class>productnrdiscount/observer</class>
                        <method>salesruleValidatorProcess</method>
                    </productnrdiscount>
                </observers>
            </salesrule_validator_process>
        </events>
    </global>
    <adminhtml>
        <events>
            <adminhtml_block_salesrule_actions_prepareform>
            <observers>
                <productnrdiscount>
                    <type>model</type>
                    <class>productnrdiscount/observer</class>
                <method>adminhtmlBlockSalesruleActionsPrepareform</method>
                </productnrdiscount>
            </observers>
            </adminhtml_block_salesrule_actions_prepareform>
        </events>
    </adminhtml>
</config>

As you can see above, there must be an Observer model that will have the two methods which modify the admin and apply the discount.

<?php
/**
 * Number of product discount module
 *
 * @author Claudiu Persoiu http://blog.claudiupersoiu.ro
 */
class CP_ProductNrDiscount_Model_Observer {

    // The new rule type
    const PRODUCT_NR_DISCOUNT = 'product_nr_discount';

    /**
     * Add the new rule type to the admin menu
     *
     * @param Varien_Event_Observer $observer
     */
    public function adminhtmlBlockSalesruleActionsPrepareform
              (Varien_Event_Observer $observer) {
        // Extract the form field
        $field = $observer->getForm()->getElement('simple_action');
        // Extract the field values
        $options = $field->getValues();
        // Add the new value
        $options[] = array(
            'value' => self::PRODUCT_NR_DISCOUNT,
            'label' => 'Product Number Discount'
        );
        // Set the field
        $field->setValues($options);
    }

    /**
     * Apply the discount
     * The discount will be applied for at least 2 products increasing
     * with a "step" for each product, where "step" is
     * maximum discount / number of products.
     *
     * @param Varien_Event_Observer $observer
     */
    public function salesruleValidatorProcess(Varien_Event_Observer $observer) {

        // $item typeof Mage_Sales_Model_Quote_Item
        $item = $observer->getEvent()->getItem();
        // $rule typeof Mage_SalesRule_Model_Rule
        $rule = $observer->getEvent()->getRule();

        // Number of products
        $qty = $item->getQty();

        // We must check the rule type in order to isolate our rule type
        if($rule->getSimpleAction() == self::PRODUCT_NR_DISCOUNT && $qty > 1) {

            // Extract rule details
            $discountAmount = $rule->getDiscountAmount();
            $discountQty = $rule->getDiscountQty();

            // Discount step
            $step = $discountAmount/$discountQty;

            // Discount calculation
            $discount = 0;
            for($i = 1; $i < $qty; $i++) {
                $itemDiscount = $i * $step;
                // If the discount is bigger then the maximum discount
                // then the maximum discount is used
                if($itemDiscount > $discountAmount) {
                    $itemDiscount = $discountAmount;
                }

                $discount += $itemDiscount;
            }
            // Effective discount
            $totalDiscountAmount = ($item->getPrice() * $discount)/100;

            // Discount in percent for each item
            $item->setDiscountPercent($discount / $qty);

            // Setting up the effective discount, basically this is the discount value
            $result = $observer->getResult();
            $result->setDiscountAmount($totalDiscountAmount);
            $result->setBaseDiscountAmount($totalDiscountAmount);

        }
    }

}

This observer will run at each request if there are items in cart that for which the rule is applicable. If the discount should be applied only for specific products, there can be filtered using the rule’s “Conditions” tab, just as you would normally do.

Written by Claudiu Persoiu

8 March 2012 at 9:37 PM

Magento native stack trace

with 5 comments

There are moments when you need to see the stack trace, to know how a certain point was reached. There are two native functions for that in PHP: debug_backtrace() si debug_print_backtrace. The first one returns an array and the second will print the stack trace to the screen.

The problem is that this functions must be customized for Magento, because it is very possible that when you’re running debug_backtrace()  you can run out of memory before you can send the output to a log file.

Magento has a native function for that purpose: Varien_Debug::backtrace([bool $return = false], [bool $html = true], [bool $withArgs = true]). In order to send the resulting stacktrace to a log file you simply all it with:

Mage::log(Varien_Debug::backtrace(true, false));

This technique is very useful when you need to see where an certain object is initialized, and what methods were executed up to that point.

Written by Claudiu Persoiu

25 February 2012 at 11:48 AM

Posted in Magento,PHP

Tagged with , , ,

Magento dead end – Breadcrumbs

without comments

In one of my adventures in the Magento code. I’ve encountered the following problem: I had to add a link to the breadcrumb.

As the documentation is not so great, after a little debugging (not a lot), I’ve got in to the core Mage_Page_Block_Html_Breadcrumbs.

The method is quite self-explanatory: addCrumb($crumbName, $crumbInfo, $after = false). Since I was there, I took a look inside:

function addCrumb($crumbName, $crumbInfo, $after = false)
{
  $this->_prepareArray($crumbInfo, array('label', 'title', 'link', 'first', 'last', 'readonly'));
  if ((!isset($this->_crumbs[$crumbName])) || (!$this->_crumbs[$crumbName]['readonly'])) {
    $this->_crumbs[$crumbName] = $crumbInfo;
  }
  return $this;
}

What’s interesting is the $after parameter, as you can see, even though it has a default value, is not used anywhere. The rest work’s as expected, probably this is why people don’t complain so much about it.

Written by Claudiu Persoiu

3 February 2012 at 10:03 PM

Posted in Magento,PHP

Tagged with ,

Another year has passed an PHP 6 remains a myth – 2011 in review

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It became a tradition for me to begin my annual review on this subject.

PHP 6 is as close to be released as it was last year, or two years ago, which is without perspective. This year PHP 5.4 reached RC4 and a final version will probably be released soon, this means that work on PHP 6 will not be resumed soon. But more about PHP 5.4 with another occasion, is on my “TODO” list to see what got into RC4.

As the main keyword for me in PHP 5.3 were namespaces, Anonymous functions, closures and garbage collector, in PHP 5.4 it seems that those keywords are going to be traits, the new closures and scalar type hinting, next to many other new features.

When I’ve wrote my first annual review blog about PHP 6, I was mainly working on Romanian websites, hence my desire for a version that will natively support this language and any other without any changes. Back then I was mainly working directly with the language, without using a framework most of the time. But since then a lot of time has passed and many things have changed, now I’m using almost exclusively frameworks and other platforms that are taking me further away from the language, offering me a different architectural perspective.

After more then an year with NCH, I’ve decided that is time for a change. This is also a company from the states with a branch in Romania, and this time is Optaros. Although I wasn’t trying to change my work place, I’ve responded to an invitation to an interview, and long story short, I left. For a long time I’ve wanted to work again for external clients, after working at NCH where all the projects were internal, I’ve wanted a change.

Again the projects are even bigger, with other scalability issues. But I think that makes web development so interesting, the bigger the scalability issues, the bigger the project.

Last year the main keywords were Linux si Symfony framework. For this year that is just ending the main keywords probably were: Magento and Drupal.

After a short period of working with Magento, I can say that it seems incredible how a platform so big has so little documentation and a lot of the time so inconsistent. It is a very complex platform and a lot of things can be done with it, but when it comes to documentation, it seems like the usual approach is to just analyze the core. Coming from the Symfony world, where there are literary books for documentation, available for free, it seems incredible how little and disorganized is the Magento documentation. But this is also a subject for another blog. A think that the Optaros team played an important role in helping me understand how to approach the issues.

Another major event for me this year was the Yahoo! Open Hack Day, event that this year was also held in Romania. I don’t think I’ve ever seen so much enthusiasm and energy in a single place, in a single day. For me as a developer it was an unforgettable experience, one of those moments that remind me why I’ve chosen this profession.

Also this year I’ve passed my PHP 5.3 certification exam, at the beginning of the year. The exam wasn’t as difficult as I’ve expected, even though the tension remains the same. The fact that it wasn’t my first certification exam helped, it’s incredible how much you remember when you start the reading the documentation again. Last year I’ve decided that I have to take at least an certification exam every year, so I have to get started on preparing for the next one.

As a conclusion, 2011 was a good year, full of challenges and accomplishments, even though I haven’t checked a lot of entries on my last year’s resolution, I’ve done quite a few that were not on that list. But now is time for another new year’s resolution.

And now I wish you an 2012 full of achievements! Happy new year!

Written by Claudiu Persoiu

3 January 2012 at 4:45 PM

Posted in Diverse

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