AJAX and PHP

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AJAX and the Future of Web Applications The hidden problem with this scenario is that each time the client needs new data from the server, a new HTTP request must be made to reload the page, freezing the user's activity. The page reload is the new evil in the present day scenario, and AJAX comes in to our rescue. Understanding AJAX AJAX is an acronym for Asynchronous JavaScript and XML. If you think it doesn't say much, we agree. Simply put, AJAX can be read "empowered JavaScript", because it essentially offers a technique for client-side JavaScript to make background server calls and retrieve additional data as needed, updating certain portions of the page without causing full page reloads. Figure 1.4 offers a visual representation of what happens when a typical AJAX-enabled web page is requested by a visitor: Figure 1.4: A Typical AJAX Call When put in perspective, AJAX is about reaching a better balance between client functionality and server functionality when executing the action requested by the user. Up until now, client-side functionality and server-side functionality were regarded as separate bits of functionality that work one at a time to respond to user's actions. AJAX comes with the solution to balance the load between the client and the server by allowing them to communicate in the background while the user is working on the page. To explain with a simple example, consider web forms where the user is asked to write some data (such as name, email address, password, credit card, etc) that has to be validated before reaching the business tier of your application. Without AJAX, there were two form validation techniques. The first was to let the user type all the required data, let him or her submit the page, and perform the validation on the server. In this scenario the user experiences a dead time while waiting for the new page to load. The alternative was to do this verification at the client, but this wasn't always possible (or feasible) because it implied loading too much data on the client (just think if you needed to validate that the entered city and the entered country match). In the AJAX-enabled scenario, the web application can validate the entered data by making server calls in the background, while the user keeps typing. For example, after the user selects a country, the web browser calls the server to load on the fly the list of cities for that country, without 14 www.it-ebooks.info
interrupting the user from his or her current activity. You'll find an example of AJAX form validation in Chapter 4. The examples where AJAX can make a difference are endless. To get a better feeling and understanding of what AJAX can do for you, have a look at these live and popular examples: Chapter 1 • Google Suggest helps you with your Google searches. The functionality is pretty spectacular; check it out at http://www.google.com/webhp?complete=1. Similar functionality is offered by Yahoo! Instant Search, accessible at http://instant.search.yahoo.com/. (You'll learn how to build similar functionality in Chapter 6.) • GMail (http://www.gmail.com). GMail is very popular by now and doesn't need any introduction. Other web-based email services such as Yahoo! Mail and Hotmail have followed the trend and offer AJAX-based functionality. • Google Maps (http://maps.google.com), Yahoo Maps (http://maps.yahoo.com), and Windows Live Local (http://local.live.com). • Other services, such as http://www.writely.com and http://www.basecamphq.com. You'll see even more examples over the course of this book. Just as with any other technology, AJAX can be overused, or used the wrong way. Just having AJAX on your website doesn't guarantee your website will be better. It depends on you to make good use of the technology. So AJAX is about creating more versatile and interactive web applications by enabling web pages to make asynchronous calls to the server transparently while the user is working. AJAX is a tool that web developers can use to create smarter web applications that behave better than traditional web applications when interacting with humans. The technologies AJAX is made of are already implemented in all modern web browsers, such as Mozilla Firefox, Internet Explorer, or Opera, so the client doesn't need to install any extra modules to run an AJAX website. AJAX is made of the following: • JavaScript is the essential ingredient of AJAX, allowing you to build the client-side functionality. In your JavaScript functions you'll make heavy use of the Document Object Model (DOM) to manipulate parts of the HTML page. • The XMLHttpRequest object enables JavaScript to access the server asynchronously, so that the user can continue working, while functionality is performed in the background. Accessing the server simply means making a simple HTTP request for a file or script located on the server. HTTP requests are easy to make and don't cause any firewall-related problems. • A server-side technology is required to handle the requests that come from the JavaScript client. In this book we'll use PHP to perform the server-side part of the job. 15 www.it-ebooks.info
Page 1 and 2: www.it-ebooks.info
Page 3 and 4: AJAX and PHP Building Responsive We
Page 5 and 6: About the Authors Cristian Darie is
Page 7 and 8: About the Reviewers Emilian Balanes
Page 9 and 10: Table of Contents Preface 1 Chapter
Page 11 and 12: Table of Contents Chapter 6: AJAX S
Page 13 and 14: Preface AJAX is a complex phenomeno
Page 15 and 16: Preface What You Need for This Book
Page 17 and 18: Preface Errata Although we have tak
Page 19 and 20: 1 AJAX and the Future of Web Applic
Page 21 and 22: Chapter 1 Because end-user satisfac
Page 23 and 24: Chapter 1 Three points for you to k
Page 25: Chapter 1 With JavaScript, develope
Page 29 and 30: • Creating simple online chat sol
Page 31 and 32: Chapter 1 done typing. (This method
Page 33 and 34: Chapter 1 All exercises from this b
Page 35 and 36: etrieve the user name $name = $_GET
Page 37 and 38: Chapter 1 If you're curious to test
Page 39 and 40: Chapter 1 request. In our case, thi
Page 41 and 42: 2 Client-Side Techniques with Smart
Page 43 and 44: AJAX Foundations: JavaScript and
Page 45 and 46: Chapter 2 • Because there is no s
Page 47 and 48: Time for Action—Using JavaScript
Page 49 and 50: Even More DOM In the previous exerc
Page 51 and 52: Chapter 2 What Just Happened? Well,
Page 53 and 54: Chapter 2 font-size: 10pt; } .Table
Page 55 and 56: Chapter 2 Creating the XMLHttpReque
Page 57 and 58: Chapter 2 You could, for example, c
Page 59 and 60: You will learn the most interesting
Page 61 and 62: Chapter 2 The safer version of proc
Page 63 and 64: Chapter 2 4. Create a file call
Page 65 and 66: Chapter 2 Figure 2.6: The Four HTTP
Page 67 and 68: Chapter 2 } } else { // display sta
Page 69 and 70: Chapter 2 } { // try to create XMLH
Page 71 and 72: Chapter 2 The responseXML method of
Page 73 and 74: Chapter 2 Figure 2.10: Opera Displa
Page 75 and 76: I admit that the following piece of
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3 Server-Side Techniques with PHP a
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Chapter 3 } for (var i=0; i
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Chapter 3 // create the element $b
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Chapter 3 // create the root eleme
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Chapter 3 // read a file from the s
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Chapter 3 Figure 3.3: PHP Parameter
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Chapter 3 Without the customized er
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} } // display the error in case of
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Chapter 3 Figure 3.7: Connecting to
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Chapter 3 } } // continue only if H
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Chapter 3 You can make Firefox list
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Chapter 3 } "MSXML2.XMLHTTP.4.0", "
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'TEXT: ' . $errStr . chr(10) . 'LOC
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etrieve the parameters $num = 1; //
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Chapter 3 Figure 3.16: Flowchart De
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} Chapter 3 // only continue if xml
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} throw(response.length == 0 ? "Ser
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function process() { // ... if (req
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Chapter 3 Working with MySQL A back
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Chapter 3 Figure 3.17: Executing SQ
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Chapter 3 SELECT user_id, user_name
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3. In your foundations folder, crea
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Chapter 3 After these commands exec
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Chapter 3 • friendly.php is a PHP
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This example requires a JavaSc
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} } // try to connect to the server
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Chapter 3 } // create HTML-formatte
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Chapter 3 On the server side, all t
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4 AJAX Form Validation Validating i
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Chapter 4 Always validate user inpu
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Chapter 4 Figure 4.4: Successful Su
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Chapter 4 .left { margin-left: 150p
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Chapter 4 value="" />
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Registration Successfull! <<
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Chapter 4 } } { // display error me
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Chapter 4 require_once ('config.php
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Chapter 4 } { } $_POST['txtBthDay']
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Chapter 4 } } ?> return ($value ==
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Chapter 4 The field ID and value re
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Chapter 4 If we are dealing with cl
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5 AJAX Chat We are living in a worl
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Chapter 5 Implementing AJAX Chat We
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Chapter 5 // default the last id to
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} Chapter 5 ' DATE_FORMAT(posted_on
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Chapter 5 AJAX Chat Your b
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* function called when the Send but
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} } // retrieve the arrays from the
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Chapter 5 } } } // call server asyn
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Chapter 5 If you analyze the code f
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The business logic behind chat.php
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6 AJAX Suggest and Autocomplete Sug
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Chapter 6 The clever part of the Ja
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Chapter 6 6. Create another file na
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Chapter 6 { } a { } font-weight: bo
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Chapter 6 } { // try to create XMLH
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Chapter 6 } } } } { } displayError(
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Chapter 6 div += "" + "" + crtFunct
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} } // select the new suggestion an
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Chapter 6 } } else // FF if (oText.
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Chapter 6 Figure 6.4: PHP Documenta
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Chapter 6 We have talked about cach
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Chapter 6 visible, we need to scrol
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7 AJAX Real-Time Charting with SVG
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Chapter 7 Figure 7.1: SVG Chart The
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Chapter 7 Figure 7.2: SVG Charting
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Chapter 7 } { xmlHttp.onreadystatec
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} } // sets the X and Y attributes
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Chapter 7 } // Supported by Mozilla
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Chapter 7 • All HTTP requests go
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8 AJAX Grid Data grids have always
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Chapter 8 Figure 8.2: AJAX Grid in
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$name = $_GET['name']; // update th
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} Chapter 8 if (!isset($_SESSION['r
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Chapter 8 # editId(, true) Edit
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Chapter 8 } // this should work for
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} Chapter 8 if(editableId) editId(e
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} color: darkblue; text-align: righ
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Chapter 8 On the client, this data
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Chapter 8 save() and undo() are hel
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9 AJAX RSS Reader In the last few y
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Chapter 9 Figure 9.1: Managing RSS
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header('Pragma: no-cache'); header(
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Chapter 9 Loading feed... Abou
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Chapter 9 } // continue if the proc
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Chapter 9 } width: 410px; backgroun
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And finally, we send the HTTP reque
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10 AJAX Drag and Drop When drag-and
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Chapter 10 The Prototype features a
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Chapter 10 When dropping a task on
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Chapter 10 DROP HERE TO DELETE
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header('Expires: Fri, 25 Dec 1980 0
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Chapter 10 } } } else if (action ==
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Chapter 10 11. Load http://localhos
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details are saved using a cache sys
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Chapter 10 Summary This is it! You'
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A Preparing Your Working Environmen
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Appendix A During installation you'
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Before going through any case studi
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Appendix A Preparing Your *nix Play
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8. Finally, point your web browser
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2. Write ajax in the Create a new d
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Index A abort() method, XMLHttpRequ
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exception handling, JavaScript, 43
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PHP Parameters and Error Handling r
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updateChart() function, realTimeCha
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AJAX and PHP

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