PHP Solutions, 3rd Edition.pdf

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Contents at a Glance

Contents

About the Author

About the Technical Reviewer

Acknowledgments

Introduction

Chapter 1: What Is PHP—And Why Should I Care?

How PHP Has Grown

How PHP Makes Pages Dynamic

Creating Pages That Think for Themselves

How Hard Is PHP to Use and Learn?

Can I Just Copy and Paste the Code?

How Safe Is PHP?

What Software Do I Need to Write PHP?

What to Look for When Choosing a PHP Editor

So, Let’s Get on with It . . .

Chapter 2: Getting Ready to Work with PHP

Checking Whether Your Website Supports PHP

Deciding Where to Test Your Pages

What You Need for a Local Test Environment

Individual Programs or an All-in-one Package?

Setting Up on Windows

Getting Windows to Display Filename Extensions

Choosing a Web Server

Installing an All-in-one Package on Windows

Setting Up on Mac OS X

Installing MAMP

Testing and configuring MAMP

Where to Locate Your PHP Files (Windows & Mac)

Using Virtual Hosts

Checking Your PHP Settings

Displaying the Server Configuration with phpinfo()

Editing php.ini

What’s Next?

Chapter 3: How to Write PHP Scripts

PHP: The Big Picture

Telling the Server to Process PHP

Embedding PHP in a Webpage

Storing PHP in an External File

Using Variables to Represent Changing Values

Naming Variables

Assigning Values to Variables

Ending Commands With a Semicolon

Commenting Scripts

Single-line Comments

Multi-line Comments

Using Arrays to Store Multiple Values

PHP’s Built-in Superglobal Arrays

Understanding When to Use Quotes

Special Cases: True, False, and Null

Making Decisions

Making Comparisons

Using Indenting and Whitespace for Clarity

Using Loops for Repetitive Tasks

Using Functions for Preset Tasks

Understanding PHP Classes and Objects

Displaying PHP Output

Using Echo Shortcut Syntax

Joining Strings Together

Working With Numbers

Understanding PHP Error Messages

Why is My Page Blank?

Handling Exceptions

PHP: A Quick Reference

Using PHP in an Existing Website

Data Types in PHP

Doing Calculations with PHP

Arithmetic Operators

Determining the Order of Calculations

Combining Calculations and Assignment

Adding to an existing string

All You Ever Wanted to Know About Quotes—and More

How PHP Treats Variables Inside Strings

Using Escape Sequences Inside Double Quotes

Embedding Associative Array Elements in a String

Avoiding the Need to Escape Quotes with Heredoc Syntax

Creating Arrays

Building an Indexed Array

Building an Associative Array

Creating an Empty Array

Multidimensional Arrays

Using Print_r( ) to Inspect An Array

The Truth According to PHP

Explicit Boolean Values

Implicit Boolean (“Truthy” and “Falsy”) Values

Making Decisions by Comparing Two Values

Testing More Than One Condition

Using the Switch Statement for Decision Chains

Using the Ternary Operator

Creating Loops

Loops Using While and Do . . . While

The Versatile for Loop

Looping Through Arrays and Objects with Foreach

Breaking Out Of a Loop

Modularizing Code with Functions

Passing Values to F unctions

Variable Scope—Functions as Black Boxes

Returning Values from Functions

Passing by Reference—Changing the Value of an Argument

Where to Locate Custom-Built Functions

Creating New Variables Dynamically

PHP Quick Checklist

Chapter 4: Lightening Your Workload with Includes

Including Code from External Files

Introducing the PHP Include Commands

Where PHP Looks for Include Files

PHP Solution 4-1: Moving the Menu and Footer to Include Files

Choosing the Right Filename Extension for Includes

PHP Solution 4-2: Testing the Security of Includes

PHP Solution 4-3: Automatically Indicating the Current Page

PHP Solution 4-4: Generating a Page’s Title From its Filename

Creating Pages with Changing Content

PHP Solution 4-5: Automatically Updating a Copyright Notice

PHP Solution 4-6: Displaying a Random Image

PHP Solution 4-7: Adding a Caption to the Random Image

Preventing Errors with Include Files

Checking the Existence of Variables

Checking Whether a Function or Class has Been Defined

Suppressing Error Messages on a Live Website

Using the Error Control Operator

Turning Off display_errors in the PHP Configuration

Turning Off display_errors in an Individual File

PHP Solution 4-8: Redirecting when an Include File Can’t be Found

Choosing where to Locate your Include Files

Adjusting your include_path

Editing the include_path in php.ini or .user.ini

Using .htaccess to Change the include_path

Using set_include_path( )

Why can’t I Use Site-root-relative Links with PHP Includes?

Document-relative Links

Links Relative to the Site Root

Links Inside Include Files

Nesting Include Files

Security Considerations with Includes

Chapter Review

Chapter 5: Bringing Forms to Life

How PHP Gathers Information from a Form

Understanding the Difference Between Post and get

Getting form Data with PHP Superglobals

Processing and Validating User Input

Creating a Reusable Script

PHP Solution 5-1: Making Sure Required Fields aren’t Blank

Preserving User Input when a Form is Incomplete

PHP Solution 5-2: Creating Sticky form fields

Filtering Out Potential Attacks

PHP Solution 5-3: Blocking Emails that Contain Specific Phrases

Sending Email

Using Additional Email Headers Safely

PHP Solution 5-4: Adding Headers and Automating the Reply Address

PHP Solution 5-5: Building the message Body and Sending the Mail

Troubleshooting mail()

Handling Multiple-Choice Form Elements

PHP Solution 5-6: Handling Radio-Button Groups

PHP Solution 5-7: Handling Check-Box Groups

PHP Solution 5-8: Using a Drop-down Option Menu

PHP Solution 5-9: Handling a Multiple-choice List

PHP Solution 5-10: Handling a Single Check Box

Chapter Review

Chapter 6: Uploading Files

How PHP Handles File Uploads

Checking whether your server supports uploads

Adding a file upload field to a form

Understanding the $_FILES array

Inspecting the $_FILES array

Establishing an upload directory

Creating an upload folder for local testing on Windows

Creating an upload folder for local testing on Mac OS X

Uploading Files

Moving the temporary file to the upload folder

PHP Solution 6-1: Creating a basic file upload script

Creating a PHP File Upload Class

Defining a PHP class

Using a namespace to avoid naming conflicts

Importing a namespaced class

PHP Solution 6-2: Creating the basic file upload class

Checking upload errors

PHP Solution 6-3: Testing the error level, file size, and MIME type

Changing protected properties

PHP Solution 6-4: Allowing different types and sizes to be uploaded

Explicitly changing a data type

Neutralizing potentially dangerous files

PHP Solution 6-5: Checking and amending filenames

Preventing files from being overwritten

PHP Solution 6-6: Renaming duplicate files

Uploading Multiple Files

How the $_FILES array handles multiple files

PHP Solution 6-7: Adapting the class to handle multiple uploads

Using the Upload Class

Points to Watch with File Uploads

Chapter Review

Chapter 7: Using PHP to Manage Files

Checking that PHP Can Open a File

Configuration Settings that Affect File Access

Creating a File Storage Folder for Local Testing

Reading and Writing Files

Reading Files in a Single Operation

PHP Solution 7-1: Getting the Contents of a Text File

Opening and Closing Files for Read/Write Operations

Reading a File with fopen( )

PHP Solution 7-2: Extracting data from a CSV file

Replacing Content with fopen( )

Appending Content with fopen( )

Locking a File Before Writing

Preventing Overwriting an Existing File

Combined Read/Write Operations with fopen( )

Moving the Internal Pointer

Exploring the File System

Inspecting a Folder with Scandir( )

Inspecting the Contents of a Folder with FilesystemIterator

Restricting File Types with the RegexIterator

PHP Solution 7-3: Building a Drop-Down Menu of Files

PHP Solution 7-4: Creating a Generic File Selector

Accessing Remote Files

Consuming News and Other RSS Feeds

Using SimpleXML

PHP Solution 7-5: Consuming an RSS news feed

Creating a Download Link

PHP Solution 7-6: Prompting a User to Download an Image

Chapter Review

Chapter 8: Generating Thumbnail Images

Checking Your Server’s Capabilities

Manipulating Images Dynamically

Making a Smaller Copy of an Image

Getting Ready

Building the Thumbnail Class

PHP Solution 8-1: Getting the Image Details

PHP Solution 8-2: Creating the Setter Methods

PHP Solution 8-3: Calculating the thumbnail’s dimensions

Using GD Functions to Create a Scaled Copy of an Image

PHP Solution 8-4: Generating the thumbnail image

Resizing an Image Automatically on Upload

Extending a Class

PHP Solution 8-5: Creating the ThumbnailUpload Class

Using the ThumbnailUpload Class

Chapter Review

Chapter 9: Pages That Remember: Simple Login and Multipage Forms

What Sessions Are and How They Work

Creating PHP Sessions

Creating and Destroying Session Variables

Destroying a Session

Regenerating the Session ID

The “Headers Already Sent” Error

Using Sessions to Restrict Access

PHP Solution 9-1: A Simple Session Example

PHP Solution 9-2: Buffering the Output with ob_start( )

Using File-based Authentication

PHP Solution 9-3: Building the Login Page

PHP Solution 9-4: Restricting Access to a Page with a Session

PHP Solution 9-5: Creating a Reusable Logout Button

Making Passwords More Secure

PHP Solution 9-6: Creating a Password-strength Checker

PHP Solution 9-7: Creating a File-based User Registration System

Checking Encrypted Passwords with password_verify()

PHP Solution 9-8: Using an Encrypted Login

Keeping Encryption Up to Date

Setting a Time Limit on Sessions

PHP Solution 9-9: Ending a Session after a Period of Inactivity

Passing Information Through Multipage Forms

PHP Solution 9-10: Using Sessions for a Multipage Form

Chapter Review

Chapter 10: Getting Started with a Database

Which Database Should You Choose?

Compatibility of MariaDB and MySQL

How a Database Stores Information

How primary keys work

Linking tables with primary and foreign keys

Breaking down information into small chunks

Checkpoints for good database design

Using a Graphical Interface

Launching phpMyAdmin

Setting Up the phpsols Database

MySQL naming rules

Case sensitivity of names

Using phpMyAdmin to create a new database

Creating database-specific user accounts

Granting user privileges

Creating a database table

Defining the images table

Inserting records into a table

Using phpMyAdmin to insert records manually

Loading the images records from an SQL file

Creating an SQL file for backup and data transfer

Choosing the Right Data Type in MySQL

Storing text

Storing numbers

Storing dates and times

Storing predefined lists

Storing binary data

Chapter Review

Chapter 11: Connecting to a Database with PHP and SQL

Checking Your Remote Server Setup

How PHP Communicates with a Database

Connecting with the MySQL Improved extension

Connecting with PDO

PHP Solution 11-1: Making a reusable database connector

Troubleshooting database connection problems

Querying the database and displaying the results

PHP Solution 11-2: Counting records in a result set (MySQLi)

PHP Solution 11-3: Displaying the images table using MySQLi

MySQLi connection crib sheet

PHP Solution 11-4: Counting records in a result set (PDO)

Counting records with PDO in other databases

PHP Solution 11-5: Displaying the images table using PDO

PDO connection crib sheet

Using SQL to Interact with a Database

Writing SQL queries

SQL is case-insensitive

Whitespace is ignored

Strings must be quoted

Handling numbers

Refining the data retrieved by a SELECT query

Selecting specific columns

Changing the order of results

Searching for specific values

Searching for text with wildcard characters

Understanding the Danger of SQL Injection

PHP Solution 11-6: Inserting an integer from user input into a query

PHP Solution 11-7: Inserting a string in MySQLi with real_escape_string()

Using Prepared Statements for User Input

Embedding variables in MySQLi prepared statements

Initialize the statement

Prepare the statement

Bind values to the placeholders

Execute the statement

Binding the results (optional)

Store the result (optional)

Fetch the result

Close the statement

PHP Solution 11-8: Using a MySQLi prepared statement in a search

Embedding variables in PDO prepared statements

Using anonymous placeholders

Using named placeholders

Preparing the statement

Binding values to the placeholders

Executing the statement

Binding the results (optional)

Fetching the result

PHP Solution 11-9: Using a PDO prepared statement in a search

PHP Solution 11-10: Changing column options through user input

Chapter Review

Chapter 12: Creating a Dynamic Photo Gallery

Why Not Store Images in a Database?

Planning the Gallery

Converting the Gallery Elements to PHP

PHP Solution 12-1: Displaying the First Image

Building the Dynamic Elements

Passing Information Through a Query String

PHP Solution 12-2: Activating the Thumbnails

Creating a Multicolumn table

PHP Solution 12-3: Looping Horizontally and Vertically

Paging Through a Long set of Records

Selecting a Subset of Records

PHP Solution 12-4: Displaying a Subset of Records

Navigating Through Subsets of Records

PHP Solution 12-5: Creating the Navigation Links

Chapter Review

Chapter 13: Managing Content

Setting Up a Content Management System

Creating the Blog Database Table

Creating the Basic Insert and Update Form

Inserting New Records

PHP Solution 13-1: Inserting a New Record with MySQLi

PHP Solution 13-2: Inserting a New Record with PDO

Linking to the Update and Delete Pages

PHP Solution 13-3: Creating the Links to the Update and Delete Pages

Updating Records

PHP Solution 13-4: Updating a Record with MySQLi

PHP Solution 13-5: Updating a Record with PDO

Deleting Records

Reviewing the Four Essential SQL Commands

SELECT

INSERT

UPDATE

DELETE

Security and Error Messages

Chapter Review

Chapter 14: Formatting Text and Dates

Displaying a Text Extract

Extracting a Fixed Number of Characters

Using the PHP substr( ) Function

Using the LEFT( ) Function in an SQL Query

Ending an Extract on a Complete Word

Extracting the First Paragraph

Displaying Paragraphs

Storing Database Records as HTML

Converting Newlines to
Tags

Creating a Function to Insert

Tags

Extracting Complete Sentences

PHP Solution 14-1: Displaying the First Two Sentences of an Article

Let’s Make a Date

How MySQL Handles Dates

Formatting Dates in a SELECT Query with DATE_FORMAT( )

PHP Solution 14-2: Formatting a MySQL Date or Timestamp

Adding to and Subtracting from Dates

PHP Solution 14-3: Displaying Items Updated within the Past Week

Inserting Dates into MySQL

PHP Solution 14-4: Validating and Formatting Dates for MySQL Input

Working with Dates in PHP

Setting the Default Time Zone

Creating a DateTime Object

Formatting Dates in PHP

Creating a DateTime Object From a Custom Format

Choosing Between Date( ) and the DateTime Class

Handling Overflows with Relative Dates

Using the DateTimeZone Class

Adding and Subtracting Set Periods with the DateInterval Class

Finding the Difference Between Two Dates with the diff( ) Method

Calculating Recurring Dates with the DatePeriod Class

Chapter Review

Chapter 15: Pulling Data from Multiple Tables

Understanding Table Relationships

Linking an Image to an Article

Altering the Structure of an Existing Table

PHP Solution 15-1: Adding an Extra Column to a Table

Inserting a Foreign Key in a Table

PHP Solution 15-2: Adding the Image Foreign Key ( MySQLi)

PHP Solution 15-3: Adding the Image Foreign Key ( PDO)

Selecting Records from Multiple Tables

PHP Solution 15-4: Building the Details Page

Finding Records that don’t have a Matching Foreign Key

Creating an Intelligent Link

PHP Solution 15-5: Returning to the Same Point in a Navigation System

Chapter Review

Chapter 16: Managing Multiple Database Tables

Maintaining Referential Integrity

Support for foreign-key constraints

PHP Solution 16-1: Checking whether InnoDB is supported

Inserting records into multiple tables

Creating a cross-reference table

Setting up the categories and cross-reference tables

Getting the filename of an uploaded image

PHP Solution 16-2: Improving the Upload class

Adapting the insert form to deal with multiple tables

PHP Solution 16-3: Adding the category and image input fields

PHP Solution 16-4: Inserting data into multiple tables

Main differences in the PDO version

Updating and Deleting Records in Multiple Tables

Updating records in a cross-reference table

PHP Solution 16-5: Adding categories to the update form

Preserving referential integrity on deletion

PHP Solution 16-6: Converting tables to the InnoDB storage engine

PHP Solution 16-7: Setting up foreign-key constraints

Creating delete scripts with foreign-key constraints

Creating delete scripts without foreign-key constraints

Chapter Review

Chapter 17: Authenticating Users with a Database

Choosing an Encryption Method

Using One-Way Encryption

Creating a Table to Store Users’ Details

Registering New Usersin the Database

PHP Solution 17-1: Creating a User Registration Form

PHP Solution 17-2: Authenticating a user’s credentials with a database

Using Two-Way Encryption

Creating the table to store users’ details

Registering new users

User authentication with two-way encryption

Decrypting a password

Updating User Details

Where Next?

Index

For your convenience Apress has placed some of the front matter material after the index. Please use the Bookmarks and Contents at a Glance links to access them. www.it-ebooks.info

Contents at a Glance About the Author �� xv About the Technical Reviewer �� xvii Acknowledgments �� xix Introduction �� xxi ■ Chapter 1: What Is PHP—And Why Should I Care? ��1 ■ Chapter 2: Getting Ready to Work with PHP ��7 ■ Chapter 3: How to Write PHP Scripts ��19 ■ Chapter 4: Lightening Your Workload with Includes ��63 ■ Chapter 5: Bringing Forms to Life ��97 ■ Chapter 6: Uploading Files ��133 ■ Chapter 7: Using PHP to Manage Files ��173 ■ Chapter 8: Generating Thumbnail Images ��207 ■ Chapter 9: Pages That Remember: Simple Login and Multipage Forms ��235 ■ Chapter 10: Getting Started with a Database ��273 ■ Chapter 11: Connecting to a Database with PHP and SQL ��299 ■ Chapter 12: Creating a Dynamic Photo Gallery ��337 ■ Chapter 13: Managing Content ��357 ■ Chapter 14: Formatting Text and Dates ��383 www.it-ebooks.info iii

■ Contents at a GlanCe ■ Chapter 15: Pulling Data from Multiple Tables ��417 ■ Chapter 16: Managing Multiple Database Tables ��435 ■ Chapter 17: Authenticating Users with a Database ��465 Index ��479 iv www.it-ebooks.info

Introduction When the first edition of PHP Solutions was published, I was concerned that the subtitle, Dynamic Web Design Made Easy, sounded overambitious. Even with this third edition, it still makes me a little apprehensive about unduly raising readers’ expectations. PHP is not difficult, but nor is it like an instant cake mix: just add water and stir. Every website is different, so it’s impossible to grab a script, paste it into a webpage, and expect it to work. My aim was to help web designers with little or no knowledge of programming gain the confidence to dive into the code and adjust it to their own requirements. The fact that the book has remained so popular since it was first published in 2006 suggests that many readers took up the challenge. Members of Boston PHP did so in large numbers when they adopted the second edition as the text for three series of PHP Percolate, a virtual self-study group for beginners. Hundreds signed up to study the book one chapter a week. It worked for them, so I hope it will work just as well for you. What’s New in this Edition One useful piece of feedback from PHP Percolate participants and other readers was disappointment when I glossed over a section of advanced code, explaining only what it did rather than how it worked. That omission has been corrected in this edition. Occasionally, I point out that you might want to skip the detailed explanation, but it’s there if you’re intrigued by how a technique works. As a result, the reference section of Chapter 3 has been expanded to include such esoteric delights as variable variables. No, it’s not a typo; “variable variable” is a genuine concept in PHP. It’s also quite useful. This edition brings the content up to date with PHP 5.6, which was released in August 2014. Because hosting companies are often slow to upgrade the version of PHP that they offer, I’ve made PHP 5.4 the minimum version for the code used in this book. PHP 5.4 made some important changes, introducing a simplified array syntax and dropping support for safe mode and “magic quotes.” As well as bringing the code up to date, I’ve revised every chapter, going through it line by line, clarifying explanations. I’ve also eliminated a number of errors—without, I hope, introducing new ones. The biggest changes are to the custom classes for uploading files and creating image thumbnails in Chapters 6 and 8. They now use namespaces to avoid naming clashes with other third-party code. More important, the class definitions have been extensively rewritten to make them more efficient. Another significant change is the use of the new password hashing functions in Chapters 9 and 17. These functions weren’t introduced until PHP 5.5, but you can emulate them in PHP 5.4 by including the password_compat library in your scripts. Details of how to obtain the library, which consists of a single file, can be found in Chapter 9. The chapters on working with a database have been reorganized to make them easier to follow. I’ve also strengthened the explanation of prepared statements, using both MySQL Improved (MySQLi) and the database- neutral PHP Data Objects (PDO). Some Linux distributions now install MariaDB as a drop-in replacement for MySQL. To avoid unnecessary repetition, I normally refer only to MySQL, but all the PHP solutions in this book work equally well with MariaDB. www.it-ebooks.info xxi

■ IntroduCtIon How This Book Is Organized Each chapter takes you through a series of stages in a single project, with each stage building on the previous one. By working through each chapter, you get the full picture of how everything fits together. You can later refer to the individual stages to refresh your memory about a particular technique. Although this isn’t a reference book, Chapter 3 is a primer on PHP syntax, and some chapters contain short reference sections—notably Chapter 7 (reading from and writing to files), Chapter 9 (sessions), Chapter 10 (data types in MySQL/MariaDB), Chapter 11 (PHP prepared statements), Chapter 13 (the four essential SQL commands), and Chapter 14 (working with dates and times). So, how easy is easy? I have done my best to ease your path, but there is no magic potion. It requires some effort on your part. Don’t attempt to do everything at once. Add dynamic features to your site a few at a time. Get to understand how they work, and your efforts will be amply rewarded. Adding PHP and MySQL/MariaDB to your skills will enable you to build websites that offer much richer content and an interactive user experience. Using the Example Files All the files necessary for working through this book can be downloaded from the Apress website at www.apress. com/9781484206362. Make sure you select the download link for PHP Solutions: Dynamic Web Design Made Easy, Third Edition. The code is different from the first two editions. Set up a PHP development environment, as described in Chapter 2. Unzip the files and copy the phpsols folder and all its contents into your web server’s document root. The code for each chapter is in a folder named after the chapter: ch01, ch02, and so on. Follow the instructions in each PHP solution, and copy the relevant files to the site root or the work folder indicated. Where a page undergoes several changes during a chapter, I have numbered the different versions like this: index_01.php, index_02.php, and so on. When copying a file that has a number, remove the underscore and number from the filename, so index_01.php becomes index.php. If you are using a program like Dreamweaver that prompts you to update links when moving files from one folder to another, do not update them. The links in the files are designed to pick up the right images and style sheets when located in the target folder. I have done this so you can use a file comparison utility to check your files against mine. If you don’t have a file comparison utility, I strongly urge you to install one. It will save you hours of head scratching when trying to spot the difference between your version and mine. A missing semicolon or mistyped variable can be hard to spot in dozens of lines of code. Windows users can download WinMerge for free from http://winmerge.org/. I use Beyond Compare (www.scootersoftware.com), which is now available for Windows, Mac OS X, and Linux. It’s not free but is excellent and reasonably priced. BBEdit on a Mac includes a file comparison utility. Alternatively, use the file comparison feature in TextWrangler, which can be downloaded free from www.barebones.com/products/textwrangler/. Layout Conventions To keep this book as clear and easy to follow as possible, the following text conventions are used throughout: Important words or concepts are normally highlighted on the first appearance in bold type. Code is presented in fixed-width font. New or changed code is normally presented in bold fixed-width font. Pseudo-code and variable input are written in italic fixed-width font. Menu commands are written in the form Menu ➤ Submenu ➤ Submenu. Where I want to draw your attention to something, I’ve highlighted it, like this: ■ ahem, don’t say I didn’t warn you. xxii www.it-ebooks.info

Chapter 1 What Is PHP—And Why Should I Care? Officially, PHP stands for PHP: Hypertext Preprocessor. It’s an ugly name that gives the impression that it’s strictly for nerds or propellerheads. Nothing could be further from the truth. A lighthearted debate on the PHP general mailing list (http://news.php.net/php.general) several years ago suggested changing what PHP stands for to Positively Happy People or Pretty Happy Programmers. This book aims to help you put PHP to practical use—and in the process help you understand what makes PHP programmers so happy. PHP is a scripting language that brings websites to life in the following ways: • • • • • • • • Sends feedback from your website directly to your mailbox Uploads files through a webpage Generates thumbnails from larger images Reads and writes to files Displays and updates information dynamically Uses a database to display and store information Makes websites searchable And much more . . . By reading this book, you’ll be able to do all that. PHP is easy to learn; it’s platform-neutral, so the same code runs on Windows, Mac OS X, and Linux, and all the software you need to develop with PHP is open source and therefore free. In this chapter, you’ll learn about the following: • • • • • How PHP has grown into the most widely used technology for dynamic websites How PHP makes webpages dynamic How difficult—or easy—PHP is to learn Whether PHP is safe What software you need in order to write PHP How PHP Has Grown PHP is now the most widely used technology for creating dynamic websites, but it started out in 1995 with rather modest ambitions—and a different name. It was originally called Personal Home Page Tools (PHP Tools). One of its main goals was to create a guestbook by gathering information from an online form and displaying it on a webpage. Within three years, it was decided to drop Personal Home Page from the name, because it sounded like something for hobbyists and didn’t do justice to the range of sophisticated features that had since been added. www.it-ebooks.info 1

Chapter 1 ■ What Is php—and Why should I Care? PHP has continued to develop over the years, adding new features all the time. According to W3Techs (http://w3techs.com/technologies/details/pl-php/all/all), PHP is used to create dynamic content by more than 80 percent of the 10 million websites it regularly surveys. It’s the language that drives highly popular content management systems (CMSs) such as Drupal (http://drupal.org/), Joomla! (www.joomla.org), and WordPress (http://wordpress.org/). It also runs some of the most heavily used websites, including Facebook (www.facebook.com) and Wikipedia (www.wikipedia.org). One of the language’s great attractions, though, is that it remains true to its roots. PHP’s original creator, Rasmus Lerdorf, once described it as “a very programmer-friendly scripting language suitable for people with little or no programming experience as well as the seasoned web developer who needs to get things done quickly.” You can start writing useful scripts without needing to learn lots of theory, yet be confident in knowing that you’re using a technology with the capability to develop industrial-strength applications. Note at the time of this writing, the current version is php 5.6. the code assumes you’re using a minimum of ■ php 5.4, which removed several outdated features, such as “magic quotes.” If you have a hosting plan, make sure the server is running at least php 5.4. the next major version of php will be called php 7. It’s been decided to skip php 6 to avoid confusion with a version that was abandoned in 2010 for being too ambitious. the emphasis in this book is on code that works now, not on what might work at some unspecified time in the future. however, I fully expect that most if not all of the code and techniques will continue to work in php 7. How PHP Makes Pages Dynamic PHP was originally designed to be embedded in the HTML of a webpage, and that’s the way it’s often still used. For example, if you want to display the current year in a copyright notice, you could put this in your footer:

On a PHP–enabled web server, the code between the tags is automatically processed and displays the year like this: This is only a trivial example, but it illustrates some of the advantages of using PHP: • • Anyone accessing your site after the stroke of midnight on New Year’s Day sees the correct year. The date is calculated by the web server so it’s not affected if the clock in the user’s computer is set incorrectly. Although it’s convenient to embed PHP code in HTML like this, it’s repetitive and can lead to mistakes. It can also make your webpages difficult to maintain, particularly once you start using more complex PHP code. Consequently, it’s common practice to store a lot of dynamic code in separate files and then use PHP to build your pages from the different components. The separate files—or include files, as they’re usually called—can contain only PHP, only HTML, or a mixture of both. 2 www.it-ebooks.info

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