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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 = 10Discount outcome:
– 0% prod 1
– 10% prod 2
…
– 50% prod 6
– 50% prod 7The first step is the module activation using the file: app/etc/modules/CP_ProductNrDiscount.xml
1<?xml version="1.0" encoding="UTF-8"?> 2<config> 3 <modules> 4 <CP_ProductNrDiscount> 5 <active>true</active> 6 <codePool>local</codePool> 7 </CP_ProductNrDiscount> 8 </modules> 9</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.
1<?xml version="1.0" encoding="UTF-8"?> 2<config> 3 <modules> 4 <CP_ProductNrDiscount> 5 <version>0.0.1</version> 6 </CP_ProductNrDiscount> 7 </modules> 8 <global> 9 <models> 10 <productnrdiscount> 11 <class>CP_ProductNrDiscount_Model</class> 12 </productnrdiscount> 13 </models> 14 <events> 15 <salesrule_validator_process> 16 <observers> 17 <productnrdiscount> 18 <type>model</type> 19 <class>productnrdiscount/observer</class> 20 <method>salesruleValidatorProcess</method> 21 </productnrdiscount> 22 </observers> 23 </salesrule_validator_process> 24 </events> 25 </global> 26 <adminhtml> 27 <events> 28 <adminhtml_block_salesrule_actions_prepareform> 29 <observers> 30 <productnrdiscount> 31 <type>model</type> 32 <class>productnrdiscount/observer</class> 33 <method>adminhtmlBlockSalesruleActionsPrepareform</method> 34 </productnrdiscount> 35 </observers> 36 </adminhtml_block_salesrule_actions_prepareform> 37 </events> 38 </adminhtml> 39</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.
1<?php 2/** 3 * Number of product discount module 4 * 5 * @author Claudiu Persoiu https://blog.claudiupersoiu.ro 6 */ 7class CP_ProductNrDiscount_Model_Observer { 8 9 // The new rule type 10 const PRODUCT_NR_DISCOUNT = 'product_nr_discount'; 11 12 /** 13 * Add the new rule type to the admin menu 14 * 15 * @param Varien_Event_Observer $observer 16 */ 17 public function adminhtmlBlockSalesruleActionsPrepareform 18 (Varien_Event_Observer $observer) { 19 // Extract the form field 20 $field = $observer->getForm()->getElement('simple_action'); 21 // Extract the field values 22 $options = $field->getValues(); 23 // Add the new value 24 $options[] = array( 25 'value' => self::PRODUCT_NR_DISCOUNT, 26 'label' => 'Product Number Discount' 27 ); 28 // Set the field 29 $field->setValues($options); 30 } 31 32 /** 33 * Apply the discount 34 * The discount will be applied for at least 2 products increasing 35 * with a "step" for each product, where "step" is 36 * maximum discount / number of products. 37 * 38 * @param Varien_Event_Observer $observer 39 */ 40 public function salesruleValidatorProcess(Varien_Event_Observer $observer) { 41 42 // $item typeof Mage_Sales_Model_Quote_Item 43 $item = $observer->getEvent()->getItem(); 44 // $rule typeof Mage_SalesRule_Model_Rule 45 $rule = $observer->getEvent()->getRule(); 46 47 // Number of products 48 $qty = $item->getQty(); 49 50 // We must check the rule type in order to isolate our rule type 51 if($rule->getSimpleAction() == self::PRODUCT_NR_DISCOUNT && $qty > 1) { 52 53 // Extract rule details 54 $discountAmount = $rule->getDiscountAmount(); 55 $discountQty = $rule->getDiscountQty(); 56 57 // Discount step 58 $step = $discountAmount/$discountQty; 59 60 // Discount calculation 61 $discount = 0; 62 for($i = 1; $i < $qty; $i++) { 63 $itemDiscount = $i * $step; 64 // If the discount is bigger then the maximum discount 65 // then the maximum discount is used 66 if($itemDiscount > $discountAmount) { 67 $itemDiscount = $discountAmount; 68 } 69 70 $discount += $itemDiscount; 71 } 72 // Effective discount 73 $totalDiscountAmount = ($item->getPrice() * $discount)/100; 74 75 // Discount in percent for each item 76 $item->setDiscountPercent($discount / $qty); 77 78 // Setting up the effective discount, basically this is the discount value 79 $result = $observer->getResult(); 80 $result->setDiscountAmount($totalDiscountAmount); 81 $result->setBaseDiscountAmount($totalDiscountAmount); 82 83 } 84 } 85 86}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.
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PHP 5.4 was released!
Even though is already yesterday news… literally, yesterday 1 March was released.
The complete list of changes is available on php.net.
I’m sorry that we still don’t have scalar type hinting in this version. The only change to type hinting was the “callable” word was added, about which I’ve talked in the closure in PHP 5.4 blog.
Another interesting thing is that this time register_globals and magic_quotes_gpc were really removed, so the old PHP 4 apps don’t get to be compatible anymore with the help of a couple of flags in php.ini.
Also the hex2bin() function was added, of course is not that important, but is interesting that the bin2hex() function existed since PHP 4. 🙂
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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 $withArgs = true]). In order to send the resulting stacktrace to a log file you simply all it with:
1Mage::log(Varien_Debug::backtrace(true, false));This technique is very useful when you need to see where an certain object is initialized, and what methods were executed up to that point.
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The concept of closure was introduced in PHP 5.3, with the new “more traditional” syntax for anonymous functions.
PHP 5.3
In PHP 5.3, a closure will rely on the term “use”, which was passing the variables to the anonymous function, making it a closure.
The problem is that the anonymous function will only be able to access the variables that have been passed with “use”. When it comes to objects, there are passed by reference by default, but scalar variables (int, string, etc.) are passed by value, as this is the default behavior in PHP 5+:
1$scalar = 5; 2 3$closure = function () use ($scalar) { 4 return 'Scalar: ' . $scalar . PHP_EOL; 5}; 6 7echo $closure(); // Scalar: 5 8 9$scalar = 7; 10 11echo $closure(); // Scalar: 5Another problem is that you cannot pass $this when the anonymous function is declared inside an object, so only the public method and properties can be accessed inside the closure.
PHP 5.4
In PHP 5.4 the keyword “use” is optional, and the entire environment where the function was created is available inside the function.
The advantage is that when the anonymous function is created inside another function or method, the anonymous function has access to the environment where it was created, even after the execution of the environment is over. The objects from this environment will be unset, only after the last reference to the closure will be unset:
1class testClass { 2 3 private $changeableVar = 1; 4 private $bigVar; 5 6 public function __construct() { 7 // Allocate a big variable so we can see the changes in memory 8 $this->bigVar = str_repeat("BigWord", 5000); 9 } 10 11 /** 12 * A method that returns the closure 13 */ 14 public function closure() { 15 16 return function () { 17 // Display the value of a private property of the object 18 echo 'Private property: ' . $this->changeableVar.PHP_EOL; 19 20 // Change the value of a private property of the object 21 $this->changeableVar = 2; 22 }; 23 } 24 25 /** 26 * Method that displays a private property 27 */ 28 public function showChangeableVar() { 29 echo 'Private property in method: ' . $this->changeableVar.PHP_EOL; 30 } 31 32} 33 34// Memory befor the objects is created 35echo "Memory: " . memory_get_usage() . PHP_EOL; // Memory: 229896 36 37// Create object 38$testObj = new testClass(); 39 40// Create closure 41$closure = $testObj->closure(); 42 43// Execute closure 44$closure(); // Private property: 1 45 46// Displaying the current value of the private property 47$testObj->showChangeableVar(); // Private property in method: 2 48 49// Memory befor object will be unset 50echo "Memory: ". memory_get_usage() . PHP_EOL; // Memory: 266240 51 52// Unset the object 53unset($testObj); 54 55// Memory after the object was distroyed, there is no big difference in memory 56echo "Memory: ". memory_get_usage() . PHP_EOL; // Memory: 266152 57 58// Run closure after the object in which it was created was unset 59echo $closure(); // Private property: 2 60 61// Unset closure and with it the object environment 62unset($closure); 63 64// Memotry after the las reference to the object (closure) is unset 65echo "Memory: " . memory_get_usage() . PHP_EOL; // Memory: 230416Callable type hinting
Another new feature introduced in PHP 5.4 regarding closures is the new “type hint”: “callable”. Actually callable is referring to any anonymous function, and even to a new way of calling a method of an object:
1<?php 2 3// A function that uses type hinting 4function typeHinting(callable $a) { 5 echo $a() . PHP_EOL; 6} 7 8// A closure 9$closure = function () { 10 return __FUNCTION__; 11}; 12 13// Call the type hinting function with the closure 14typeHinting($closure); // {closure} 15 16class testClass { 17 public function testMethod() { 18 return __METHOD__; 19 } 20} 21 22// A mock object 23$testObj = new testClass(); 24 25// The new way of calling object methods 26$objCallable = array($testObj, 'testMethod'); 27 28// Call type hinting function with the new method calling way 29typeHinting($objCallable); // testClass::testMethodI believe that only now we can really say that PHP supports closures, the right way!
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In one of my adventures in the Magento code. I’ve encountered the following problem: I had to add a link to the breadcrumb.
As the documentation is not so great, after a little debugging (not a lot), I’ve got in to the core Mage_Page_Block_Html_Breadcrumbs.
The method is quite self-explanatory: addCrumb($crumbName, $crumbInfo, $after = false). Since I was there, I took a look inside:
1function addCrumb($crumbName, $crumbInfo, $after = false) 2{ 3 $this->_prepareArray($crumbInfo, array('label', 'title', 'link', 'first', 'last', 'readonly')); 4 if ((!isset($this->_crumbs[$crumbName])) || (!$this->_crumbs[$crumbName]['readonly'])) { 5 $this->_crumbs[$crumbName] = $crumbInfo; 6 } 7 return $this; 8}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.