Graphics by Greg

I just put together my first simple website for my new toy - my iPhone. It is a simple iPhone-specific interface for Yelp, my favorite source for restaurant and other local reviews. They have a ton of reviews for just about every local restaurant so I find myself using it all the time to find new restaurants to go to or to find more info about restaurants I already know. I could access the website just fine already on my phone, but it was a bit crowded and difficult to navigate on a small screen, so I decided it take this as a challenge to build my first iPhone web interface.

And yes, I’m probably about the 58th person to build a Yelp interface for the iPhone, but I was looking for something I’d actually use and learn from!

Yelp provides a REST search API that allows you to pass in a location and a search term and they return a JSON object with a list of matching businesses, their ratings, and the business info. I used the Zend Framework and the Prototype JavaScript library to put it together. I could have done a pure JavaScript implementation using script hacks, but figured it’d be better to have the PHP code serve as a basic proxy for the Yelp web service.

Try it out!

I put together a simple, lightweight PHP class for generating thumbnail images. The class is compatible with PHP5 and uses the GD2 extension (included by default with PHP5) to create JPEG, PNG, and GIF thumbnails. I've setup a Google Code project for it: Gregphoto_Image where you can checkout the source from SVN and file bugs.

The class has the following basic features:

• Ability to read JPEG, PNG, or GIF images
• Ability to output JPEG, PNG, or GIF images
• 4 modes of thumbnail creation
  • MAX_HEIGHT - you specify a maximum height and the dimensions are calculated based off of the height
  • MAX_WIDTH - you specify a maximum width and the dimensions are calculated based off of the width
  • BEST_FIT - you specify a maximum height and width and the dimensions are calculated so that the thumbnail
    is as large as possible without exceeding the maximum height or width
  • EXACT - you specify a maximum height and width and these are directly used. Causes distortion if the
    chosen aspect ratio is different from the aspect ratio of the image
• Renders/saves images in their input format by default, but allows changing the format. For example, input a GIF but output a PNG
• Fully documented object oriented code
• Fluent interface for creating thumbnails with a minimal amount of code

The class is licensed under the MIT license, which basically means it can be used and modified by anyone - for personal or commercial use.

You can Download it from the project page on Google Code. You can view examples of it running on my site - the examples are checked into SVN and can be viewed on the project site. You can also view the docs.

Example usage:

Enjoy!

Overview

The following is an example of a simple reusable widget created using the Prototype JavaScript library. The widget is an 'accordian' - a widget composed of multiple sections, of which only one is open at a time. This type of widget is available in all sorts of applications, from Microsoft Outlook (circa Outlook 2000), to web applications, and more. In addition to showing off this simple widget, I'd like to walk through it to explain how it works and how to write something like this with Prototype. For all of Prototype's greatness, there is certainly a lack of documentation that makes it a little bit difficult to get into.

Example

Take a look at the example page I put together showing a few examples of accordians and their capabilities. This article will explain how to put together the class that does this.

Explaination: Creating Reusable Classes

I'll skip with going through the HTML - you can see that on the example page if you're interested - it would be helpful in understanding the javaScript here. In this example I've used version 1.5.0_rc0 of Prototype. The first line of the accordian.js file has the following:

Prototype's Class.create() sets up Accordian as an object that can be instantiated. When the object is instantiated the 'initialize' method, its constructor, will be automatically called. You setup all of the methods within the object by defining its prototype - an object with properties and methods. This could be done in the following way:

This object could be instantiated in the following way:

Explanation: Writing the Constructor

The constructor needs to take two arguments - the ID of the element that contains the accordian and the type of entry that is used for the header of each section. The constructors main job is getting a list of all of the sections within the accordian and adds onClick event handlers to the headers so that clicking them will open the section. The constructor is shown below:

Now to explain what's going on in the constructor:

• The first line defines the function that expects two variables - the ID of the element that holds the accordian and the type of element that will serve as the header for a section.
• The second line sets a class property, 'container', to the element passed in with variable 'elem'. It uses Prototype's $() function, which in this case is equivalent to document.getElementById()
• The third line uses the very powerful $$() function that returns an array of all elements that match a given css query. In this case, the query might look like '#myAccordian .section h3', which would return all h3 elements under an element with class 'section' under the element with ID 'myAccordian'.
• Lines 4-6 setup the event handlers that will be used when the user clicks the headers. This uses the each() function that Prototype adds to arrays in order to quickly loop through an array without using a for loop or creating a bunch of temporary variables. This function takes a function as an argument that will be applied as an iterator over the array. This use of this technique is similar to the foreach concept in PHP (foreach($headers as $header)) and other languages. Because functions are objects in JavaScript, we need to add a trick at the end of the each function defined within 'each' - we need to add 'bind(this)'. This means that within the new function, the 'this' keyword will be bound to the Accordian object, not to the function itself.
• Line 5 uses Prototype's Event class to setup the observer - in this case it will bind the classes sectionClicked method to any click on the header elements. Similar to the binding needed on the function, the reference to the sectionClicked function is follwed by 'bindAsEventListener(this)', which means that inside the event handler, 'this' will refer to the Accordian object, not to the clicked header element.

Explanation: Writing the Event Handler

The function referenced as the event handler in the constructor is shown below:

Functions called as an event always get passed an event object. This function takes this event and uses the Prototype 'Event' class to get a handle on the parent node of the element that was clicked, the section itself. It then passes this as an argument to another method in this class - openSection.

Explanation: Opening a Section

This function if fairly straightfoward - it checks to see if the section being opened is already open, and if not, calls a function to close the open section, and finally opens the new section. It is shown below:

• The function takes one argument, the section that is to be opened
• The second line uses the $() function to get the DOM element. It is important to note that this function can either take the section ID as an argument or the actual section DOM node. The $() function adds this extra flexibility
• The third line checks to see whether the ID of the section is the same as the currently open section. If it is, no other logic is performed. If it isn't, the next few lines will open that section.
• After line 4 calls a function to close the existing section, line 5 sets a class property 'currentSection' to the new section
• Line 6 uses Prototype's getElementsByClassName, passing the class (contents) and the element under which it should look (the new section). This returns an array of elements
• Line 7 takes the first element with class contents (their should only be one), and uses Prototype's show() function to show the element

Explanation: Closing a Section

This last function is the simplest of all - it checks to see whether there is an open section, and if so, it hides it.

• The second line checks if the currentSection exists - it is only set after the first section has been opened
• The third line uses the same technique as in the previous function - it uses getElementsByClassName to get the elements with class 'section'
• Finally, the hide function will hide this element so that the section is collapsed

The Final Script

Conclusion

Though this is a fairly simple example, I hope it helped to explain some of the features of the Prototype library and can get people kickstarted to writing classes with JavaScript. Most of it is very simple...if only there were some real documentation. The best source right now is probably Developer notes for prototype.js, which covers features up to Prototype 1.4. Another site with a compilation of links is http://www.prototypedoc.com/.

Go forth and rid the world of nasty IE5 style, unreadable, browser-sniffing, hackish, global-scope JavaScript!

Recently I put together a reusable Ajax form validation component that I'd like to share. It is a JavaScript object that collects the values of all of the elements in a form, sends it for processing to the server, and displays any errors. If there are no errors it submits the form. There are several benefits to this approach

• Allows you to perform complex validation, such as verifying the uniqueness of a username, or checking something in the database...all without reloading the page
• Allows you to use the same validation routine for both client-side validation and server-side validation
• Reduces the amount of client-side code needed for validation

The JavaScript used in my example requires the Prototype library. My example uses PHP to perform the validation - more specifically, I've used several components of the Zend Framework (PHP5 only). The example uses:

• Zend_Controller_* classes including the new RewriteRouter to handle the routing within the application
• Zend_View to handle the output
• Zend_View_Helper_* classes to build form elements
• Zend_Config to read in configuration options
• Zend_Filter to perform several field validations
• Zend_Json to serialize PHP variables/objects to JSON objects

Did I need all of this stuff on the server-side to put together a simple form validation example? Heck no, but when I'm experimenting with new stuff I like to use a lot of new components so I can learn more about them and be prepared for when I actually do need to use all of this fire power. I've been following the Zend Framework carefully, so I wanted to use some of the stuff I hadn't used yet - particularly the controller architecture.

The HTML and JavaScript

Ok, back to how this JavaScript is used. It's actually really quite simple. First, you need to include the JavaScript files for both Prototype and AjaxFormValidator in the head of your HTML document:

Next, you add an 'onSubmit' handler to the form you'd like to validate - in this case, mine looks like this:

The form action is set to the page I'd like the script to go to if the validation is successful. The onSubmit calls a custom function that we still need to define. It passes 'this' as an argument - the 'this' refers to the form element itself.

Now we define the submitForm() function that the onSubmit of the form will call - it looks like the following:

This function first creates a new AjaxFormValidator object, passing it the form element (or the form id) and the url the validation request should be sent to. The next two lines setup the type of error display that should happen. The following error display types are supported:

• alert: The default option. Displays all errors in a JavaScript alert box.
• inline: Displays errors within an element that is defined on the page. You need to set the element name with validator.inlineElem. In this example, errors will be shown in a div with id="errorDiv".
• none: errors won't be shown to the user. The will be available as an array of errors in the errors property of the validator (i.e. validator.errors). If there are no errors the property will be set to false. Once you have the errors you can perform more advanced error handling/display to the user.

Lastly, validator.validate() will send the values in the form, in an HTTP POST, to the validation url you've provided (/ajaxValidate/index/validate in this case). If there are no errors the form will be submitted, if there are errors the will be shown (or not shown if you've chosen 'none' as the errorDisplay).

The PHP

Once the request is sent it will eventually arrive at the server for processing - in this case, through the magic of routing, it is going to end up in my IndexController in the validateAction method. This function is shown below:

This function calls another method within the IndexController class called getErrors, passing in the entire array of POST arguments (values in the form). It receives back an array full of error strings. If there are no errors, it changes the value of the $error variable to false. Lastly, it uses Zend_Json to convert the PHP array/Boolean into the equivalent JavaScript array/Boolean. This string is printed and sent back to the client.

The getErrors function itself is very straightforward - it just does a couple validations and returns back an array of the errors.

Check it out, in action. And that's about it - pretty simple, huh?

You can download:

• The JavaScript
• The whole PHP project

Having put together a couple websites (Redstone Studios and Althea) that integrate with Paypal for providing checkout capabilities, I was very interested to look at Google Checkout when it was released this past week. My experience with the Paypal integration was not so good - while I eventually got it to work, it took a ton of experimentation, searching for documentation, and guessing why things weren't working (i.e. no meaningful error messages). Luckily, Google Checkout doesn't seem to suffer from these problems - I had it up and running in no time and it seems very solid for what it does. What does it do? Well, it's basically a checkout system where you can pass in a cart, users can pay by credit card, and then the money gets deposited in your bank account. Google charges 2% of the transaction amount plus twenty cents. The two percent covers the percent Google has to pay the credit card companies, and the twenty cents is some extra cash for Google. If you use Google Adwords, you get a free credit on Google Checkout - for every 1 dollar spent on Adwords you get 10 dollars of sales with no costs.

Google provides sample PHP code for getting the integration going, but unfortunately the code is PHP4 only, and it is ugly ugly ugly code. I decided to put together a simple class that allows simple integration with Google Checkout. The class is PHP5 only because it uses PHP5's DOM extension.

To use Google Checkout you need to create a Google Checkout account. From there, you can get your merchant id and merchant key, both of which are needed to communicate with Google Checkout. The Google Checkout API works by POSTING XML over HTTP. While Google's API is very flexible, I've chosen to implement a subset that I think would be useful for many people. Also, I've only implemented this class to support the creation of the cart and submission to Google, I haven't included any functionality for greater integration. This greater integration would involve creating web services that Google could call to update the website on changes to the order status, shipping, etc. The way I've set this up, all of that is skipped, and store owner would receive orders via email or Google's Checkout interface.

Limitations:

• No support for cart expiration
• No support for merchant calculations for tax/shipping/gift certificates as these require HTTPS and I don't have it and don't care to use it
• No support for requesting the buyers phone number because I didn't notice that field until just now!
• No support for shipping restrictions - i.e. shipping option 1 is only available in these zip codes/states/etc
• No support for complicated tax rules. Tax can be setup on a state by state basis. One alternative tax rule 'taxfree' is setup to allow certain items to be tax free. No support for other alternative tax rules.
• Currently doesn't support customization of the form and checkout image

In order to work around some of these limitations, I've provided a method called setDefaultXML which allows the developer to specify a default XML file to be used. The class will then fill in the items, do the encryption, and generate the form and checkout image. This allows much greater flexibility and support for all of Google's options, when needed.

Here's a simple example of how I might use it:

Now, for what's going on:

• Line 1 includes the class
• Lines 3 and 4 setup variables for the merchant id and merchant key
• Line 6 instantiates the class, passing in the merchant id and key
• Line 7 sets the class to use the Google Checkout Sandbox - this is a testing sandbox where you can setup fake accounts to use while creating your site. Paypal offerers a much richer sandbox functionality.
• Lines 8-11 add new line items to the cart, setting there name, description, price, quantity, notes, and special tax rules
• Lines 12 and 13 setup the URLs the user should be sent to if the choose to edit the cart or continue shopping
• Lines 14-16 setup various shipping options including their prices
• Lines 17 and 18 setup taxes for the users in specific states. Google Checkout supports much richer rules around taxation, but I kept it simple on a state-by-state level.
• Line 20 outputs the HTML form and checkout image that will send the cart to Google Checkout and bring the user to the Google Checkout page
• Line 21 shows the XML cart, for debugging purposes

View this example running on my site
View the API of Gregphoto_Service_Google_Checkout
Download the class and API docs
View Google's Develper Guide for Google Checkout