Posts tagged PHP

I am a ‘plugged’ person, means that I am constantly connected to the net and being a member of a certain number of social networks and tools (I maybe a weirdo but *no facebook* account) and I am very surprised of the amount of people that are highly interested on Yii and asks information on what is the best way to learn the framework. In order to solve those doubts I would like to put my two cents on this matter by sharing with you what was my learning curve with Yii -this way I do not need to post in every social network I am involved with.

For this post I assume that you know PHP (beginner, intermediate) and some DB skills for whatever the DB Engine you prefer to work with (MySQL, Oracle, etc…)

Yii Learning Guide

When you first arrive to Yii’s website, even though is an amazingly easy to navigate and use Website, you will obviously feel lost and won’t know where to start working with, and this is the most important steps of them all: download and READ its Definitive Guide to Yii. Do not worry if you do not understand some concepts, but you need to read it all, do not let any episode without a look as you will soon understand everything and will get ‘hooked’ by the easiness and magic of Yii. If you prefer not to download it, an online version of the guide is also available. If you are new to MVC, then I also recommend the visit to Larry Ullman’s Learning Yii Series blog.

After the guide, you will have tons of questions to solve and, even though will become a great tool in the future, do not jump immediately on the forum to drop them all. You need to get your hands on a practical example and for that, the demo application of The Yii Blog Tutorial is the perfect playground. It is highly recommended that you have your preferred PHP editor with two projects open: one that is the full demo blog application that comes with the Yii Framework download package, and the practical project that you will create following the tutorial. There are a couple of lines of code that you need to discover in the builded demo application and there are not in the tutorial.

There is also a book, “Agile Web Application Development with Yii1.1 and PHP5“, that takes you step-by-step through the process of using a test-driven development (TDD) approach to develop a real world Web application with Yii, from initial concept through production-readiness. This is another good practical tutorial to follow. If you do buy the book, then I recommend you to subscribe to Yii’s forum and follow this discussion: http://www.yiiframework.com/forum/index.php?/topic/11920-identified-issues/.

If you have reached this far on the article and follow the above steps then you are already amazed of Yii’s power and probably started your first real-world project with the Framework. Real issues and challenges will arise, it is time to find out about Yii’s amazing network of people, register and subscribe to Yii’s forum. Ask and you will be answered, people are so helpful and polite, it is just unreal the response time of this community. If you prefer  to get immediate help, then use Yii’s live IRC chat.

Don’t think that your learning curve has stopped here, to be ‘plugged’ to the network is highly recommended, so ‘plug’ your self to the Wiki. Its articles are written by other fellow programmers, it is a programmers-to-programmers experience, and due to the nature of the people that are part of this network, the Wiki grows day-by-day. This is the reason that I am subscribed to its RSS. You can also stay up to date by following any of the next social networks accounts: Twitter, Facebook or LinkedIn

Once you know the ins and outs of the Framework, one great learning resource are the Extensions written by other programmers. Use them in order to easy your tasks and solve your problems but also read at its guts, its code behind. You will be surprised on how much you can learn from that. If you do not understand something within that code, have *always* a browser window or a tab opened with Yii’s Class Reference.

If you are comfortable with PHP, then I also recommend that you look at the code of the Framework. For example, if you wish to display a radio button using CHtml::radioButton look at the function itself too. Lots of forum questions wouldn’t be posted if they follow this simple advice.

Final Words

There are other resources to take into account (resources directly extracted from Yii’s site):

Cheat Sheets

The Yii cheat sheet, created by Sebastián Thierer. This presents commonly used Yii classes, methods and properties in a single printable sheet.

Yii 1.1 validator cheatsheet: created by schmunk. This summarizes all of Yii’s built-in validators in a single printable sheet.

Yii Playground

The Yii Playground is a community-contributed demo application that uses the PHP Yii Framework to show some features of the framework by explicit example. It is great place to see how some of the features work, and learn the code behind them.

Radio Podcasts

Yii Radio Podcasts, created by Imre Mehesz, covers hot topics and recent activities about the Yii framework.

Blogroll

The community-driven wiki page Yii Related Sites is collecting links to sites with useful tips and tutorials related to the Yii Framework.

The most important thing is that, once you get your hands on this amazing framework you get actively involved in the community (Forum, Wiki, Extensions), and share your projects so others can look at Yii’s real power and provide you with positive feedbacks.

I truly hope this article provides you with an easy guidance to get into Yii’s framework.

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First of all let’s find out what is exactly a behavior in Yii’s language (text extracted from Yii’s Definitive Guide):

A behavior is an object whose methods can be ‘inherited’ by its attached component through the means of collecting functionality instead of specialization (i.e., normal class inheritance). A component can be attached with several behaviors and thus achieve ‘multiple inheritance’.

Behavior classes must implement the [IBehavior] interface. Most behaviors can extend from the CBehavior base class. If a behavior needs to be attached to a model, it may also extend from CModelBehavior or CActiveRecordBehavior which implements additional features specifc for models.

This means that if we require additional features to the models we could extend them by using behaviors and also, that a model could actually implement more than one behavior thus extending endlessly its functionality.

Behaviors is the answer to those who wish to do things that differ from normal use and they need to be shared among other models but not to all of them. What that means? Well, IMHO, I think that if you need a special functionality that is shared among model objects then I suggest that would it better that you create a class that extends from the CActiveRecord and then extend your models from it.

I heard so many times that people wishes to create functions in controllers and we should stick to the MVC approach as it is, and not try to reinvent the wheel with things that come out our creative minds. If you need to do specific actions thing about a controller but if that action involves DB data then work with Models. This is a long discussion that could hold an article by itself; let’s be focus with this article.

Building and Using a Behavior

Our behavior will transform a model into a JSON array and as the Yii guide says, it implements the IBehavior interface as it extends from CBehavior. The code is extracted from my own extension behavior EJsonBehavior, here it is:

//
// EJsonBehavor extends from CBehavior
class EJsonBehavior extends CBehavior{
//
// this property will hold a reference to
// its owner - the model class that will
// have this behavior attached to it
private $owner;
//
// this property will reference the
// relations of the model class -owner
private $relations;
public function toJSON(){
//
// getting a reference to model class
// having this behavior attached to it
$this->owner = $this->getOwner();
//
// making sure it is a CActiveRecord descendant
if (is_subclass_of($this->owner,'CActiveRecord')){
//
// play with it!
//
// get model attributes
$attributes = $this->owner->getAttributes();
//
// if this model has related model classes
// get them attributes
$this->relations 	= $this->getRelated();
//
// structure the to-be-converted JSON
$jsonDataSource = array('jsonDataSource'=>array('attributes'=>$attributes,'relations'=>$this->relations));
//
// return the JSON result
return CJSON::encode($jsonDataSource);
}
return false;
}
//
// returns related model's attributes
private function getRelated()
{
$related = array();
$obj = null;
$md=$this->owner->getMetaData();
foreach($md->relations as $name=>$relation){
$obj = $this->owner->getRelated($name);
$related[$name] = $obj instanceof CActiveRecord ? $obj->getAttributes() : $obj;
}
return $related;
}
} // end of class

The important thing about the above code is not the funcitonality exposed, converting the model to a JSON array, but how we could get a hold to the behavior’s parent and access all its properties. That means, that by the same technique we could use that reference (owner) to play with the database referred by the object itself (check for example the code of the SLUG behavior).

Attaching the Behavior to a Model

This is the easiest part -yes, it is true, writing behaviors is a pretty easy thing with Yii. One way is the one referred on the wiki, which is the way I use it when I just need the use of a behavior certain times but the way I mostly use them is like this:

//
// This function is in the model
// where we want to attach the
// behavior too
public function behaviors() {
//
// needs to return an array
// of behavior objects
return array(
'EJsonBehavior'=>array(
//
// please check how it says to Yii
// where the class is located
'class'=>'application.behaviors.EJsonBehavior'
),
);
}

In the code above, you see how I tell Yii where the class is located in my applications folder; in this case I say to Yii to look for our behavior in the protected/behaviors folder and inside it there is a file EJsonBehavior.php which holds a behavior with a class name as the name of the file -EJsonBehavior.

Once we have attached the behavior to our model class, to use it is as simple as to call its public methods and/or properties. With our behavior above, we just do:

//
// pfff, so easy...
echo $model->toJSON();

After you have seen how easy is to create behaviors, having a look to the code of the Behaviors list at Yii’s site, will incredibly help your current learning curve. Hope this article has helped you to better understand behaviors.

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Trying to learn and help some other programmers to find their solutions on the Yii Forum (I think is a superb way to learn the framework), I was facing one challenge with an external library that a fellow programmer wanted to use -quite good indeed: PHPExcel . And what is PHPExcel?

PHPExcel – OpenXML – Create Excel2007 documents in PHP – Spreadsheet engine

Project providing a set of classes for the PHP programming language, which allow you to write to and read from different file formats, like Excel 2007, PDF, HTML, … This project is built around Microsoft’s OpenXML standard and PHP.

Checkout the Features this class set provides, such as setting spreadsheet meta data (author, title, description, …), multiple worksheets, different fonts and font styles, cell borders, fills, gradients, adding images to your spreadsheet and much, much more!

The Challenge

The fellow programmer (Jack Fiallos) had a problem of using the libraries within Yii. He was surprised that he could easily use the libraries outside of the framework but not within the framework itself. At first we didn’t think about it but suddenly we thought about the autoloading features of Yii and looked into the guts of PHPExcel to find out what was causing the problems.

We were right, PHPExcel has an autoloading feature itself that when a classes is called (i.e. PHPExcel_Shared_ZipStreamWrapper) the first part of the name is actually reflecting the folder’s path where the class is located (i.e. PHPExcel_Shared_ZipStreamWrapper = PHPExcel/Shared_ZipStreamWrapper.php). Please review the following code (extracted from PHPExcel_Autoloader class):

public static function Load($pObjectName){
    if ((class_exists($pObjectName)) || (strpos($pObjectName, 'PHPExcel') === False)) {
       return false;
    }
    // this is the code that shows what I am saying
    $pObjectFilePath =  PHPEXCEL_ROOT.
           str_replace('_',DIRECTORY_SEPARATOR,$pObjectName).'.php';
           if ((file_exists($pObjectFilePath) === false) || (is_readable($pObjectFilePath) === false)) {
		return false;
           }
	require($pObjectFilePath);
}	//	function Load()

Solution

The workaround to this problem (at least the one I know) is by making use of the spl_autoload_register and spl_autoload_unregister PHP’s functions. The following code shows how we got the library working -I assume that you have downloaded the PHPExcel files, unzipped its contents and place them into a phpexcel folder within your application’s protected/extensions folder:

//
// VERY DUMMY TEST CONTROLLER
// FOR THE SAKE OF THE EXAMPLE
// TEST IT AS http : / / <yourapplicationurl> / index.php ? r=test/test
class TestController extends Controller{
     // no layouts here
     public $layout = '';
     public function actionTest()
     {
     //
     // get a reference to the path of PHPExcel classes
     $phpExcelPath = Yii::getPathOfAlias('ext.phpexcel.Classes');
     // Turn off our amazing library autoload
      spl_autoload_unregister(array('YiiBase','autoload'));
     //
     // making use of our reference, include the main class
     // when we do this, phpExcel has its own autoload registration
     // procedure (PHPExcel_Autoloader::Register();)
    include($phpExcelPath . DIRECTORY_SEPARATOR . 'PHPExcel.php');
     // Create new PHPExcel object
     $objPHPExcel = new PHPExcel();
     // Set properties
     $objPHPExcel->getProperties()->setCreator("Maarten Balliauw")
							 ->setLastModifiedBy("Maarten Balliauw")
							 ->setTitle("PDF Test Document")
							 ->setSubject("PDF Test Document")
							 ->setDescription("Test document for PDF, generated using PHP classes.")
							 ->setKeywords("pdf php")
							 ->setCategory("Test result file");
     // Add some data
     $objPHPExcel->setActiveSheetIndex(0)
            ->setCellValue('A1', 'Hello')
            ->setCellValue('B2', 'world!')
            ->setCellValue('C1', 'Hello')
            ->setCellValue('D2', 'world!');
      // Miscellaneous glyphs, UTF-8
     $objPHPExcel->setActiveSheetIndex(0)
            ->setCellValue('A4', 'Miscellaneous glyphs')
            ->setCellValue('A5', 'éàèùâêîôûëïüÿäöüç');
      // Rename sheet
      $objPHPExcel->getActiveSheet()->setTitle('Simple');
      // Set active sheet index to the first sheet, so Excel opens this as the first sheet
     $objPHPExcel->setActiveSheetIndex(0);
      // Redirect output to a client’s web browser (Excel2007)
      header('Content-Type: application/pdf');
      header('Content-Disposition: attachment;filename="01simple.pdf"');
      header('Cache-Control: max-age=0');
      $objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'PDF');
      $objWriter->save('php://output');
       //
       // Once we have finished using the library, give back the
       // power to Yii...
       spl_autoload_register(array('YiiBase','autoload'));
       }
}

Final Words

This post is using PHPExcel external library as an example, but this procedure should be taken into account when we encounter a problem like this. Whenever you find a library that you wish to include in your Yii application, check out its autoloading functions first.

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