Showing error on my custom module in magento

Question

I working now in magento for developing a module to check the voucher code used or not. The details are stored in a new table. In my config.xml, I specified the observer page for fetching the details from db table. But I don't know the exact use of observer page in magento. Can I use observer page for this usage.

But it proceed to an error I checked the log file:

a:5:{i:0;s:203:"SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '=' at line 1";i:1;s:1677:"#0 C:\wamp\www\Mymagento\lib\Varien\Db\Statement\Pdo\Mysql.php(110): Zend_Db_Statement_Pdo->_execute(Array)

My observer.php file is also shown below

class Module_Voucher_Model_Observer {
    public function __contruct() {
        $coupon_code = trim(Mage::getSingleton("core/session")->getData("coupon_code"));
    }

    public function getresultofVoucher($coupon_code) {
        $resource = Mage::getSingleton('core/resource');
        $readConnection = $resource->getConnection('core_read');
        $table = "voucher_code_status_table";
        $query = 'SELECT * FROM ' . $table. 'WHERE value='.$coupon_code;
        $results = $readConnection->fetchAll($query);

        return $results;
    }
}

and my Indexcontroller.php shown below:

class Module_Voucher_IndexController extends Mage_Core_Controller_Front_Action {
    /**
    * Coupon code checking
    **/
    public function indexAction() {
        $this->loadLayout();
        $block = $this->getLayout()->createBlock('Mage_Core_Block_Template','vouchercode',
        array('template' => 'voucher/vouchercode.phtml')
        );
        $this->getLayout()->getBlock('left')->append($block);
        $this->renderLayout();
    }

    public function CheckAction() {
        $coupon_code = $this->getRequest()->getParam('coupon_code');
        //$coupon_code ='63663';
        if ($coupon_code != '') {
            Mage::getSingleton("core/session")->setData("coupon_code",$coupon_code);     //("checkout    /session")->
        }
        else {
            //
            //echo 'error : Voucher code issue';
        }
        if ($this->getRequest()->getParam('url')) {
            header('HTTP/1.1 301 Moved Permanently');
            $gclid = $this->getRequest()->getParam('');
            $url = $this->getRequest()->getParam('url');
            header('Location: /' . $url . '?voucherbox=' . $gclid);
            die();
        }
        else {
            $this->_redirect("/");
        }
    }
}

I think there is no option to call the observer page function in controller page.

Answer 1

@SIBI A, I am just trying to answer about use of observers.

Observers are mainly used to add more functionalities/Change some existing behaviours at the time of a particular event happens in magento application flow.

Prior to concentrating on observer, we should have an understanding on various events which are observable in magento. For example "sales_order_place_after" is an event fired by magento while it places a new order.

If you search for a string "Mage::dispatchEvent" inside a magento root folder, you can see a lot of statements which fire various kinds of events on different occassions.

Let's consider the following scenario. Its just an example for understanding the basic concept.

Scenario: We need to update the "customer_note" field in sales_flat_order table while a customer places a new order.(NB:sales_flat_order is the table which saves basic information about each orders)

Even though there may exist a lot of conventional approaches to accomplish this functionality, we can do this by means of a new observer also. Let me write some basic steps of the process

1. Create a module
2. Create a model class
3. Add an observer method, which listens to the event "order_place_after"
4. Define the observer method, access the $order object inside this method
5. Update the "customer_note" field in $order object and save.

If the above steps are done and working fine, when we place a new order we can see that "customer_note" column(in sales_flat_order table) have the value updated via our new observer method.

If you check the function place() inside Mage_Sales_Model_Order class, you can see there magento fires the event "sales_order_place_after" to which we are listening. It is passing the current $order object to the event as parameter. We will get this $order object in our observer method as parameter because we are listening to this particular event.

I am giving here the files which might be used to create the module to accomplish the above.

1) app/etc/modules/Research_OrderCustomerNoteModify.xml

<?xml version="1.0"?>
<config>
 <modules>
  <Research_OrderCustomerNoteModify>
   <active>true</active>
   <codePool>local</codePool>
  </Research_OrderCustomerNoteModify>
 </modules>
</config>

2) app/code/local/Research/OrderCustomerNoteModify/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Research_OrderCustomerNoteModify>
            <version>0.1.0</version>
        </Research_OrderCustomerNoteModify>
    </modules>
    <global>
        <models>
            <research_ordercustomernotemodify>
                <class>Research_OrderCustomerNoteModify_Model</class>
            </research_ordercustomernotemodify>
        </models>
        <events>
            <sales_order_place_after>
                <observers>
                    <research_ordercustomernotemodify_update_customernote_field>
                        <class>research_ordercustomernotemodify/observer</class>
                        <method>updateCustomernoteField</method>
                    </research_ordercustomernotemodify_update_customernote_field>
                </observers>
            </sales_order_place_after>
        </events>
    </global>
</config>

3) app/code/local/Research/OrderCustomerNoteModify/Model/Observer.php

<?php
class Research_OrderCustomerNoteModify_Model_Observer
{
    public function updateCustomernoteField($observer)
    {
        $order = $observer -> getEvent() -> getOrder();
        $currentNote = $order->getCustomerNote();
        $order->setCustomerNote('Customer has quoted this'.$currentNote);
        $order->save();
        return;
    }
}

Answer 2

Normally, observers are used to do some operation by listening to certain events. For example while doing check out, if we need to modify some tables after saving the order, we will listen to the event sales_order_place_after and create an observer class and method in our module. But still if u need to call the observer method you wrote above, you can create an instance of that server class and access the method

• $obj = new Module_Voucher_Model_Observer()
• $obj->getresultofVoucher