Web Database Applications with PHP, and MySQL

Arrays

Arrays in PHP are sophisticated and more flexible than in many other high-level languages. An array is an ordered set of variables, in which each variable is called an element. Technically, arrays can be either numbered or associative , which means that the elements of an array can be accessed by a numeric index or by a textual string, respectively.

In PHP, an array can hold scalar values—integers, Booleans, strings, or floats—or compound values—objects and even other arrays, and can hold values of different types. In this section, we show how arrays are constructed and introduce several useful array functions from the PHP library.

Creating Arrays

PHP provides the array( ) language construct that creates arrays. The following examples show how arrays of integers and strings can be constructed and assigned to variables for later use:

$numbers = array(5, 4, 3, 2, 1);
$words = array("Web", "Database", "Applications");

// Print the third element from the array 
// of integers: 3
echo $numbers[2];

// Print the first element from the array 
// of strings: "Web"
echo $words[0];

By default, the index for the first element in an array is 0. The values contained in an array can be retrieved and modified using the bracket [ ] syntax. The following code fragment illustrates the bracket syntax with an array of strings:

$newArray[0] = "Potatoes";
$newArray[1] = "Carrots";
$newArray[2] = "Spinach";

// Oops, replace the third element
$newArray[2] = "Tomatoes";

Numerically indexed arrays ...