Sandlight CMS V: Functional Protective Proxy Login

loginOn this blog, the Protective Proxy pattern has several different implementations, and if you’d like to refresh your memory, this post has the foundation upon which the others are built. The design pattern for the Proxy is relatively simple: the user logs into a site, and instead of going directly to the subject page, users are sent to a Proxy subject where their credential are checked. If the Proxy page determines valid credentials (typically a username and password), the user is sent to the subject page where the content resides.

With an administrative login, the work to be done (in this case) is to add and edit dynamic content for a page. The upper right portion of the main page is made up of materials that come from a database so that adding and changing content is relatively simple. However, before even getting to the administrative editing portion of the CMS, you want to be sure that only those with permission have access to the dynamic editor. So this post deals only with the login portion of the CMS. Go ahead and test it and download the source files:
PlayDownload

Rats! I forgot to tell you the username and password. You can find them in the source code in the download or in this post; so go ahead and dig them up and try again. It will help you understand how this proxy implementation works.

The Functional Protective Proxy

As noted above, other examples of the Proxy design pattern have been used and explained elsewhere on this blog. In this (protective) Proxy implementation, only one feature has changed: the methods are all written using functional programming protocols. Figure 1 shows the design pattern diagram for this implementation of the Proxy.

Figure 1: Class diagram for Protective Proxy

Figure 1: Class diagram for Protective Proxy

As far as protective Proxys go, this one is not unusual. The ReLog could have been handled by sending the user back to the LoginUI, but by having a different looking UI, it helps the user pay attention a bit more prior to re-entering the username and password. The path it follows is pretty simple:

  1. LoginUI: User enters username and password.
  2. LoginClient: Sends login request to LoginProxy.
  3. ILogin: Sets up two abstract methods and a concrete method along with encoded usernames and passwords. It also provides several protected properties. Both the LoginProxy and Login classes implement (extend) this abstract class interface
  4. LoginProxy: Evaluates username and password and sends it to Login if correct and ReLog if not.
  5. Login: Calls AdminUI (to be developed).
  6. ReLog: Re-start process requesting user name and password.

You can obscure the password and username better than I did for this example of the Proxy implementation. When used in an actual environment, you can store the codes in a special MySql table, a Json file, a text file or even a hidden element in an HTML5 document. Since users are not going to be logging in, other than the site administrator, you should be sure that they cannot even find where to log in! It’s a lot easier than trying to protect a site where users are expected to login.

When you look at the different classes, you won’t see much functional programming except in LoginProxy class. That’s because, there’s not a lot of code in any of the classes. The UI (LoginUI and ReLog) classes create and display HTML pages, the client class calls the proxy class (LoginProxy) but it’s the LoginProxy that has to do all of the thinking. Using functional operations, primarily lambda functions (PHP anonymous functions), the class methods determines what to do next: send on the request to the Login object or reroute it to the start-over class, ReLog. That’s pretty much it. In looking at the LoginProxy class code, you can see the functional operations at work:

< ?php
class LoginProxy extends ILogin
{
	//Proxy Subject
	public function doLogin()
	{ 	
		$this->sun=$_GET['username'];
		unset($_GET['username']);
		$this->spw=$_GET['password'];
		unset($_GET['password']);
 
		try
		{
			$this->security=$this->setPass();
			$this->igor=$this->sun==base64_decode($this->security[0]) && $this->spw==base64_decode($this->security[1]);
			$lambda=function($x) {$alpha=$this->igor ? $this->passSecurity=true : NULL; return $alpha;};
			$lambda($this->igor);
			$this->loginOrDie();
		}
 
		catch(Exception $e)
		{
			echo "Here's what went wrong: " . $e->getMessage();
		}
	}
 
	protected function loginOrDie()
	{
		$badPass=function($x) {$delta= $x ? ($this->goodLog=new Login()) : ($this->badLog=new ReLog());};
		$badPass($this->passSecurity);
		$goodPass=function($x) {$tau= $x ? ($this->goodLog->doLogin()) : NULL;};
		$goodPass($this->passSecurity);
	}
}
?>

Using the two methods implemented from the ILogin interface (abstract class), doLogin() and loginOrDie(), the functions work to determine whether 1) the password and username are correct and 2) send the request to the correct object: Login or ReLog.

What functional programming seems to do, among other things, is to create a series of binary queries with Booleans. For example, the protected variable $igor ($this->igor) has a double boolean assigned to it whereby two (2) comparative statements must resolve to true. By doing so, $igor becomes a Boolean value. (Who’s the Boolean now?! Snap!) Next, $igor, is a Boolean, as an argument in a lambda function ($lambda) determines whether the $passSecurity variable is to be changed from false to true—yet another Boolean!

In the loginOrDie() method, the $passSecurity variable is used again—this time as an argument—in the the $badPass() and $goodPass() lambda functions. That’s how this implementation of the protective Proxy determines whether the password and username are valid. The same determination could have been done using imperative conditional statements (e.g., if, switch), but in moving towards more functional programming within design pattern structures, the functional statements accomplish the same task with non-imperative programming.

In looking at the Login class, what is referenced as the “Real Subject” in design patterns, it does little more than pass the request to a user interface where the actual administration work can be done.

< ?php
class Login extends ILogin
{
	//Real Subject
	public function doLogin()
	{ 
		$this->loginOrDie();
	}
 
	protected function loginOrDie()
	{
		$admin=new AdminUI();
		$admin->dataStrat();
	}
}
?>

A tighter implementation would have us place the UI for the Administration module in the Login itself, but we’re not striving for “tightness.” Rather, this code moves a loosely bound module in a Proxy pattern to the next module using a Strategy pattern. As you will see in the interface used by both the LoginProxy and Login classes, the Login class only implements the two abstract methods and uses none of the other other protected properties or method. Continue reading ‘Sandlight CMS V: Functional Protective Proxy Login’

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Sandlight CMS IV: Dynamic Responsive Web PHPages

responsiveAt this point in the Sandlight CMS development process, two design patterns have been employed: 1) Chain of Responsibility as a device checker, and 2) Abstract Factory for making different parts for different devices. As usual, I’ve been posting the results so far on the Sandlight Productions, LLC website. The site itself is the example used in this series. This post is Part IV of the Sandlight CMS series, and if you have not been following the series you can review what has been done so far beginning with Part I.

At this stage, the project is ready to use the Abstract Factory to produce the needed parts and put them together into a page. However, before going ahead and have the factory build the parts I’d like to take an intermediate step and just build a dynamic responsive Web page.

The Dynamic Responsive Web PHPage

The easiest way to proceed is to begin with an HTML5 page, encapsulate the page into a PHP object (class) and add methods. The reason for this step is that the Web site, in addition to being responsive, needs to be dynamic. This means that it needs a way for the administrator to add changes, and in order for this to transpire, the dynamic portion of the page has to include variables in the place of static text, graphics and/or video. Figure 1 shows the general layout envisioned for the page:

Figure 1: Dynamic Responsive Web Page

Figure 1: Dynamic Responsive Web Page

Everything about the page must be responsive, but some parts are static and some are dynamic. In the two-column outline in Figure 1, the entire left column is static yet it must be responsive to different devices. In Parts I to III of this series, the pages have been responsive. The next step in making them both responsive and dynamic is to create parts of the page that will be dynamic since they are already set up to be responsive. Before continuing, click the Play button to see the progress so far and the Download button for all of the source code and accompanying files:
PlayDownload

Using PHP alone, creating a dynamic page is simple. Just place PHP variables where content goes. This is true for both the pages formatted by CSS3 and jQuery. Importantly, though, all of the Web pages should be encapsulated into PHP classes, using heredoc string variables as has been shown in previous installment of this series.

QR Code: The New Responsive Component

Quick Response Code (QR) is a new necessity for Web sites doing business on the Web and for just about every other kind of site that wants to increase its exposure. Basically, using a QR Code reader in a mobile device (phone or tablet) automatically brings up the link coded in the QR image (a square with some squiggly block images.) That beats trying to to thumb in a URL on a tiny phone keyboard. The following two can be downloaded free (at the time of this writing.):

sandlightqrcodeI’m pretty certain that other smart phones have QR readers; so if you have something other than an iOS or Android operating system on your mobile device, an Internet search for “QR Scanner” will probably be able to locate one for you.

sandlightOnce you have a QR scanner, you need a coded image, such as the one to your right. Go ahead and scan it to see what happens. It should take you to the Sandlight Productions, LLC home page build on this CMS (updated.) On it you will find several more QR codes for links to sites related to Sandlight. You can get the coded images online at different sites. One site allows you to include your logo and choice of colors is QRCode Monkey. The QR code image in green to your left with the Sandlight logo in the middle does exactly the same thing as the black one. So, if you’d like your QR Code images to keep your graphic designer happy, consider the visual options beyond the default. Figure 2 shows a page being scanned with an iPhone (left) and the linked page in the iPhone (right).

Figure 2: Scanned QR URL uploaded in mobile phone.

Figure 2: Scanned QR URL uploaded in mobile phone.

Adding QR codes to your site (or your client’s site) is very easy, and you should definitely include it in your dynamic responsive CMS. Let’s now see how the dynamic responsive two-column page is created:
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Sandlight CMS III: PHP Abstract Factory

abfacNote: This is the third in a series for developing a CMS for Sandlight Productions. Drop by the Sandlight site to see the progress so far, and be sure to check your country’s flag count!

Now that the CMS has a filter for different devices, it now needs a pattern to take care of those devices and different types of content that they will display. Previous posts on this blog used the Bridge pattern and the Factory Method pattern. However, another pattern might be more useful for all of the different things that a Content Management System (CMS) might do. A review of the series of posts on this blog for how to select a design pattern, shows the different criteria to consider. The CMS has to create different elements of a Web page for different devices and that fact must be the focal point of the consideration. The section head for Creational Patterns in Learning PHP Design Patterns, lists the Abstract Factory pattern as a creational one, but that pattern was not discussed in the book nor on this blog. It would appear to be just what this CMS needs.

The Abstract Factory Design Pattern

The Abstract Factory pattern has features for families of factories and products instead of individual factories as does the Factory Method pattern. In comparing the relatively simple Factory Method pattern with the Abstract Factory, the Abstract Factory has multiple abstract product interfaces with multiple concrete factories for the families of the products.

Figure 1 shows the the Abstract Factory class diagram, and when you look at it, try to focus on the fact that the pattern has two types of interfaces: Factory and Product. So, if you understand the Factory Method pattern, you have a starting point for appreciating the Abstract Factory:

Figure 1: Abstract Factory class diagram

Figure 1: Abstract Factory class diagram

Unlike the Factory Method pattern, the Abstract Factory includes a Client class as an integral part of the pattern. Further, the Client holds an association between both the AbstractFactory (AbsFactory) and the two AbstractProduct classes. So while it shares some of the basic Factory Method characteristics, it is clearly a different pattern than the Factory Method.

Since the Abstract Factory may appear to be daunting, the color-coded the product instantiations (dashed lines) in the file diagram (appearing in the Play window) help show where each concrete factory method calls. Experiment with different combinations of factories (devices) and products (page parts) and look at the diagram so that you can see the path. Phone instantiations are in green, Tablet in red, and Desktop in blue. Experiment with the different single products first, and then click the bottom button to see what different “pages” each device factory displays.

Implementing the Abstract Factory in PHP

To see how this implementation of the Abstract Factory design pattern works, click the Play button. You will see both the interactive Abstract Pattern tester and the of the file diagram of this implementation of the Abstract Factory for the evolving Sandlight CMS. Click the Download button to see all of the files in the diagram. For this particular post, downloading all of the files is more important than usual because there are lots of them, and rather than having listings for all in this write-up, I’ve just selected representative ones.
PlayDownload

In addition to the Abstract Factory file diagram (viewed when you click the Play button), the following quick overview of the participants’ roles and how the CMS implements the Abstract Factory explain how this implementation works:

Client client: Only uses interfaces declared by IAbFactory (interface) and IProducts (abstract classes IHeaderProduct, IImageProduct and ITextProduct.) This means that the Client can only use the classes and methods implemented from those two interface types—factory or products. In other words, it should not directly implement a product (a page element) by directly using a product independent of the factory and product interfaces. Figure 2 illustrates this point:

Figure 2: Client works through Abstract Factory implementations

Figure 2: Client works through Abstract Factory implementations

In going over the other participants below, keep in mind that the Client can only implement concrete implementations of the IAbFactory to request products (page parts for different devices.)

IAbFactory interface: Establishes the methods for the concrete factories.

  • PhoneFactory implements operations to create phone products
  • TabletFactory implements operations to create tablet products
  • DesktopFactory implements operations to create desktop products

IHeaderProduct: abstract class Establishes the method for concrete header products and adds protected property for returning completed product.

  • PhoneHeader defines phone object to be created by the PhoneFactory and
    implements the IHeaderProduct interface
  • TabletHeader defines tablet object to be created by the Tabletactory and
    implements the IHeaderProduct interface
  • DesktopHeader defines desktop object to be created by the DesktopFactory and
    implements the IHeaderProduct interface

IImageProduct: abstract class Establishes the method for concrete image and/or video products and adds protected property for returning completed product.

  • PhoneImage defines phone object to be created by the PhoneFactory and
    implements the IImageProduct interface
  • TabletImage defines tablet object to be created by the Tabletactory and
    implements the IImageProduct interface
  • DesktopImage defines desktop object to be created by the DesktopFactory and
    implements the IImageProduct interface

ITextProduct: abstract class Establishes the method for concrete text products and adds protected property for returning completed product.

  • PhoneText defines phone object to be created by the PhoneFactory and
    implements the ITextProduct interface
  • TabletText defines tablet object to be created by the Tabletactory and
    implements the ITextProduct interface
  • DesktopText defines desktop object to be created by the DesktopFactory and
    implements the ITextProduct interface

Comparing the above outline with the Abstract Factory file diagram (seen when you click the Play button) shows that the Abstract Factory is bound to the idea of a factory implementing a product. The specific classes (products) requested are never directly referenced by the Client; rather it is through a factory. The CMS application requires factories for the different device categories; Phone, Tablet and Desktop. Each factory should be able to build the necessary parts (products) for each device. In this case (and for this example) the products are a Header, Graphic and Text. Each factory can build its own version of the products; so requesting a header, for example, is through a concrete factory, and depending on which concrete factory the clients requests, it builds the appropriate product.
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Sandlight CMS II : Mobile First!

mobileFirstI’m not a graphic designer, and so I depend on others for the graphic elements and arrangement of my Web pages. However, I strive to make a site that is clear, easy to understand and useful. My focus is on good user experience (UX) and information design—clear communication with the user. In order to have good UX, you need to know something about Responsive Web Design (RWD), and if you don’t, check out the RWD link. Further, if you are unfamiliar with the approaches to RWD, I’m sold on the Mobile First approach, but possibly for different reasons than designers. Let me explain.

In designing my own site, my focus is on content categories, ease of maintenance, which includes updates and changes, and device flexibility. So I have to keep all of those in mind. I want PHP to handle regular updates by using content from a MySql database (the Content Management of CMS), and I need it to work on different devices. By tackling mobile first, I have to create a diamond-tipped focus on exactly what I want the user to view because even with the new “Phablets,” I’m not dealing with a lot of screen real estate. Currently, my old working mobile phone has a CSS resolution of 320 x 480, and my Phablet is 414 x 736. That’s less that 100 units different. (By CSS resolution, I’m referring to what CSS reads as far as screen width is concerned. See this table.)

Choosing the Devices

In an another sniffer program using a Chain of Responsibility (CoR) design pattern and a PHP user agent ($_SERVER['HTTP_USER_AGENT']) posted on this blog, the sniffer detected the user agent and then found the handler responsible for that agent. Now that user agents have been replaced by CSS screen width (as determined by a JavaScript function) for determining the device, we can use the same CoR pattern making the necessary changes. However, instead of getting real pages, we can use stand-ins that only have the roughest page content. All of the content will be encapsulated into PHP classes using heredoc strings. Near-future posts cover the mechanics of working out the MySql to provide dynamic content for the pages, along with other details necessary for the CMS. For now, though, the dummy pages will only contain enough material to demonstrate that each is appropriate for the selected device. Use the buttons below to see the current state of the CMS and download the files for this portion:
PlayDownload

Note that all devices can now access the Flag Counter. Where is your country on the Flag Counter? (See the note about the Flag Counter at the end of this post.)

Back to the Chain of Responsibility Pattern (CoR)

The CoR pattern is handy because it’s easy to update and change. For example, suppose that having three device categories (e.g., phone, tablets and desktops) proves to be inadequate and you want to add two more; one for laptops and another for phablets. It’s a simple matter to add to the chain and add device classes to handle the new devices. Figure 1 shows the first design pattern to be used in the CMS:

Figure 1: Chain of Responsibility Implementation

Figure 1: Chain of Responsibility Implementation

In Part I of this series, you can see how the device width and height is determined using a JavaScript closure (object) to pass the information to HTML and on to PHP. Since we only need to find the width, the JavaScript code has been slightly altered and placed in a separate file (deviceCatcher.js) in case it needs to be reused.

?View Code JAVASCRIPT
//deviceCatcher.js
function getWide()
{
	var wide = screen.width;
	return function()
	{
		return wide;
	}
}
var w = getWide();
//Send data to PHP class, CoRClient.php	
var lambdaPass= function() {window.location.href = "CoRClient.php?hor=" + w();};

The HTML file simply calls the closure function which passes the values to PHP:

<html>
	<head>
		<title>Device Catcher</title>
		<script src="deviceCatcher.js" type="text/javascript"></script>
	</head>
	<body onload=lambdaPass()>
	</body>
</html>

The HTML file is a trigger to get the ball rolling with the client class (CoRClient).

Starting the Chain

The client pulls the viewing device’s width from the superglobal, and passes it to a PHP variable. Given the variability in the width of device screens, I made the decision to work with three sizes to get started: 1) phone, 2) tablet, and 3) desktop. So, depending on the width, the request would be handled by one of those three device groups. I used the following cutoff sizes:

  1. Phone: >= 480
  2. Tablet: >=481 and < 900
  3. Desktop: >= 900

I used this table as a guide, but cutoff points can be anything you want.

Getting the width from the superglobal is easy enough using a static variable:

self::$wide=$_GET['hor'];

The, using the cutoffs, the program needs to generate three strings, phone, tablet, and desktop to send to the Request class that stores the appropriate string. The most obvious way is to use conditional statements (if or switch) to generate the correct string for Request. For example an imperative algorithm such as the following would do the trick:

if(self::$wide < = 480)
{
	return "phone";
}
elseif (self::$wide >= 900)
{
	return "desktop";
}
else
{
	return "tablet";
}

However, a functional program would be more compact, and like the JavaScript closure used in Part I, it would be an “object.” Transformed into a functional closure, the operation would look like the following:

$beta = self::$wide >= 900 ? 'desktop' : 'tablet';
$lambda = function($x) use ($beta) {
	$alpha =  $x < = 480 ? 'phone' : $beta;
	return $alpha;};

Using ternary operations ?: , $alpha and $beta both have function-like qualities. for example, $beta could have been written as a function beta() as shown in Figure 2:

Figure 2: "Functional" variables

Figure 2: “Functional” variables

As you can see in Figure 2, $beta provides the same functionality as beta(), and $beta can be used as a reference in the $lambda function along with $alpha in a PHP closure. (For some reason, when $beta is assigned an anonymous function, I was unable to get it to be added as a closure in the $lambda anonymous function.)
Continue reading ‘Sandlight CMS II : Mobile First!’

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Sandlight CMS I: Device Closures

devicesIn previous posts on this blog, I’ve included PHP patterns that deal with the issue of creating sites for multiple devices. In developing a Content Management System (CMS) for my Sandlight site, I wanted to start from scratch and use both elements of OOP and design patterns as well as functional programming. (Functional programmers may furrow their collective brows and mutter You’re ruining FP, but there’re enough arguments among FP advocates, that I’m not overly concerned.)

The Problem with User Agents

The problem with user agents (UAs) such as $_SERVER['HTTP_USER_AGENT'] in PHP, is that the information they provide is insufficient. For example, if you get “trident” from a user agent, it could be anything from a Microsoft-based computer to a MS phone. Devices identified as “iPad” can be the iPad Minis or the full-size iPads. And of course, if you get “Android” or “iPhone,” it can be any size screen from the early smart phones to what some call “Phablets”— the big phones like iPhone 6+ and Galaxy Note 3. To get started, take a look at this table. Not only will that table give you a range of mobile devices, it provides the way in which browsers communicate the type of device currently reading a page. (The CSS column is the most relevant for setting up a CMS that will adjust to different devices.)

How Can You Get the Screen Size for PHP?

If you’ve used CSS3, you are familiar with CSS media queries where you can direct the CSS to different classes and IDs depending on the screen size. It’s just as easy using JavaScript. The built-in document properties, screen.width and screen.height can be passed to variables and in turn to PHP. The procedure is a simple one-line program:

<script>
  window.location.href = "WiHi.php?hor=" + screen.width + "&vert=" + screen.height;
</script>

The JavaScript variables are hor and vert and can retrieved in PHP using $_GET[‘hor’] and $_GET[‘hi’]. So while that code can be saved as an html file and pass the data to a PHP class, it also offers up an opportunity to demonstrate how to add functional programming (FP) to JavaScript and to use FP with OOP. Use the buttons to test the program on as many devices as you have to see the range of screen sizes. Download the complete file set as well:
PlayDownload

Instead of stopping here and announce Mission Accomplished, I’d like to consider functional programming in JavaScript and closures in particular. In order to understand why I think it’s important to do this, consider the general purpose of both OOP design patterns and functional programming. Both were developed to better organize programming so that larger programs (consider what goes into your favorite game program) can be developed, maintained and changed.

Hackers vs Programmers

Hackers and hacks have a history of unthoughtful and malicious programming. It takes talent to build a house, but none to burn one down. The term “hack” originated as a program created by programmers who just threw code at a problem until something worked. The problem with hacks and hackers is that while the short-term goals may be accomplished, especially with short programs, hacks are like a guy with a machete chopping his way through the jungle to make a trail. The next time he comes down the trail, it’ll be grown over, and he’ll have to hack a new path. Figure 1 illustrates creating a hack vs. creating a program:

Figure 1: Hacking vs. Programming

Figure 1: Hacking vs. Programming


Compared to a modern highway, where planning, use of structure and interactive cooperation can create something of lasting value, hacks are a one-time accomplishment. It’s a kid playing in the mud. Fun until he’s got to start cleaning his own clothes.

Functional Programming in JavaScript

As you probably know, JavaScript does not have classes per se, and so we’re not going to try to create an OOP class in JS. However, the JavaScript folks are fortunate in having the book, Functional JavaScript (O’Reilly, 2013) by Michael Fogus. Functional programming is an important framework to understand in both PHP and JavaScript, and you can find a number of articles and other works covering FP in JS in addition to the Fogus book.

The “objects” in FP are called closures. In variations on JS and in special FP libraries (e.g., Underscore.js) you can find more FP functionality just as in the Hack dialect of PHP has functional operations for PHP not found in standard PHP. However, for here, I’d like to stick to plain vanilla JS and create what Fogus referred to as a “closure simulators” (faux closures), but they serve the same purposes. (PHP also has closures and a built-in Closure class.) I tend to think of closures as FP “objects,” but that characterization has a number of fuzzy edges; however, it’s a convenient way to think about them. Fogus summarizes a closure

as a function that captures the external bindings (i.e., not its own arguments) contained in the scope in which it was defined for later use (even after that scope has completed.)

—Michael Fogus p. 60, Functional JavaScript (O’Reilly, 2013)

A bit more dramatic description by Fogus is,

Closures are the programming language equivalent of vampires—they capture minions and give them everlasting life until they themselves are destroyed. The only difference is that closures don’t sparkle when exposed to sunlight.
—Michael Fogus p. 61, Functional JavaScript( O’Reilly, 2013)

Unfortunately, the PHP manual describes closures as equivalent to anonymous functions or lambdas. Simon Holywell in Functional Programming in PHP (p. 33) clarifies the manual’s misconception by noting that PHP closures are functional structures that include the use clause. In any event, both Holywell and Fogus describe a type of “object” where data can be packaged and used elsewhere in a program. So let’s take a look at a closure in JavaScript:

<html>
	<head>
		<title>Passing Width & Height with Closure</title>
		<script type="text/javascript">
			//Use closure "objects" to store screen size
			function getWide()
			{
				var wide = screen.width;
				return function()
				{
					return wide;
				}
			}
			function getHi()
			{
				var hi = screen.height;
				return function()
				{
					return hi;
				}
			}
 
			//Pass closures to variables
			var w = getWide();
			var h = getHi();
 
		        //Send data to PHP class, WiHi.php	
			var lambdaPass= function() {window.location.href = "WiHi.php?hor=" + w() + "&vert=" + h();};
		</script>
	</head>
	<body onload=lambdaPass()>
	</body>
</html>

The two functions, getWide() and getHi() are simulated closures, but functionally, they work just like closures. In fact, they work pretty much like objects. These two closures are passed to variables, w and h, which themselves are then closures and can be used to return the width and height of the device screen. Continue reading ‘Sandlight CMS I: Device Closures’

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