History and Evolution of PHP: Hypertext Preprocessor

PHP stands for “PHP: Hypertext Preprocessor” where “Preprocessor” means that changes happen before the HTML page is created. This converts static webpage to dynamic webpage with the capacity to interact with databases. The PHP programming language is commonly used for developing web-based software applications. However, the use of the language is not limited to web development [ ...] [ ...]

PHP’s Place in the Web World

PHP is a programming language that’s used mostly for building websites. Instead of a PHP program running on a desktop computer for the use of one person, it typically runs on a web server and is accessed by lots of people using web browsers on their own computers. This section explains how PHP fits into [ ...] [ ...]

What’s So Great About PHP?

You may be attracted to PHP because it’s free, because it’s easy to learn, or because your boss told you that you need to start working on a PHP project next week. Since you’re going to use PHP, you need to know a little bit about what makes it special. The next time someone asks [ ...] [ ...]

PHP in Action

Ready for your first taste of PHP? This section contains a few program listings and explanations of what they do. If you don’t understand everything going on in each listing, don’t worry! That’s what the rest of the book is for. Read these listings to get a sense of what PHP programs look like and [ ...] [ ...]

Basic Rules of PHP Programs

This section lays out some ground rules about the structure of PHP programs. More foundational than basics such as “How do I print something?” or “How do I add two numbers?” these proto-basics are the equivalent of someone telling you that you should read pages in this book from top to bottom and left to [ ...] [ ...]

Data: Working with Text in PHP

When they’re used in computer programs, pieces of text are called strings. This is because they consist of individual items, strung together. Strings can contain letters, numbers, punctuation, spaces, tabs, or any other characters. Some examples of strings are I would like 1 bowl of soup, and “Is it too hot?” he asked, and There’s [ ...] [ ...]

Data: Working with Numbers in PHP

Numbers in PHP are expressed using familiar notation, although you can’t use com­mas or any other characters to group thousands. You don’t have to do anything spe­cial to use a number with a decimal part as compared to an integer. Example 2-15 prints some valid numbers in PHP. Example 2-15. Numbers print 56; print 56.3; [ ...] [ ...]

Data: Working with Variables in PHP

Variables hold the data that your program manipulates while it runs, such as user information that you’ve loaded from a database or entries that have been typed into an HTML form. In PHP, variables are denoted by a $ followed by the variable’s name. To assign a value to a variable, use an equals sign [ ...] [ ...]

Logic in PHP: Understanding true and false

Every expression in a PHP program has a truth value: true or false. Sometimes that truth value is important because you use it in a calculation, but sometimes you ignore it. Understanding how expressions evaluate to true or false is an important part of understanding PHP. Most scalar values are true. All integers and floating-point [ ...] [ ...]

Logic in PHP: Making Decisions

With the if() construct, you can have statements in your program that are only run if certain conditions are true. This lets your program take different actions depend­ing on the circumstances. For example, you can check that a user has entered valid information in a web form before letting her see sensitive data. The if() [ ...] [ ...]

Logic in PHP: Building Complicated Decisions

The comparison and logical operators in PHP help you put together more compli­cated expressions on which an if() construct can decide. These operators let you compare values, negate values, and chain together multiple expressions inside one if() statement. The equal operator is == (two equals signs). It returns true if the two values you test [ ...] [ ...]

Logic in PHP: Repeating Yourself

When a computer program does something repeatedly, it’s called looping. This hap­pens a lot—for example, when you want to retrieve a set of rows from a database, print rows of an HTML table, or print elements in an HTML <select> menu. The two looping constructs discussed in this section are while() and for(). Their specifics [ ...] [ ...]

Groups of Data: Array Basics in PHP

An array is made up of elements. Each element has a key and a value. For example, an array holding information about the colors of vegetables has vegetable names for keys and colors for values, as shown in Figure 4-1. An array can only have one element with a given key. In the vegetable color [ ...] [ ...]

Groups of Data: Looping Through Arrays in PHP

One of the most common things to do with an array is to consider each element in the array individually and process it in some way. This may involve incorporating it into a row of an HTML table or adding its value to a running total. The easiest way to iterate through each element of [ ...] [ ...]

Groups of Data: Modifying Arrays in PHP

You can operate on individual array elements just like regular scalar variables, using arithmetic, logical, and other operators. Example 4-18 shows some operations on array elements. Example 4-18. Operating on array elements $dishes[‘Beef Chow Foon’] = 12; $dishes[‘Beef Chow Foon’]++; $dishes[‘Roast Duck’] = 3; $dishes[‘total’] = $dishes[‘Beef Chow Foon’] + $dishes[‘Roast Duck’]; if ($dishes[‘total’] > [ ...] [ ...]

Groups of Data: Sorting Arrays in PHP

There are several ways to sort arrays. Which function to use depends on how you want to sort your array and what kind of array it is. The sort() function sorts an array by its element values. It should only be used on numeric arrays, because it resets the keys of the array when it [ ...] [ ...]

Groups of Data: Using Multidimensional Arrays in PHP

As mentioned in “Array Basics” on page 57, the value of an array element can be another array. This is useful when you want to store data that has a more complicated structure than just a key and a single value. A standard key/value pair is fine for matching up a meal name (such as [ ...] [ ...]

Groups of Logic: Declaring and Calling Functions in PHP

To create a new function, use the function keyword, followed by the function name and then, inside curly braces, the function body. Example 5-1 declares a new function called page_header(). Example 5-1. Declaring a function function page_header() { print ‘<html><head><title>Welcome to my site</title></head>’; print ‘<body bgcolor=”#ffffff”>’; } Function names follow the same rules as variable [ ...] [ ...]

Groups of Logic: Passing Arguments to Functions in PHP

While some functions (such as page_header() in the previous section) always do the same thing, other functions operate on input that can change. The input values sup­plied to a function are called arguments. Arguments add to the power of functions because they make functions more flexible. You can modify page_header() to take an argument that [ ...] [ ...]

Groups of Logic: Returning Values from Functions in PHP

The header-printing function you’ve seen in this chapter takes action by displaying some output. In addition to an action such as printing data or saving information into a database, functions can also compute a value, called the return value, which can be used later in a program. To capture the return value of a function, [ ...] [ ...]