Arrays in PHP

An array is list of values that can be referenced with a single variable. This is achieved by using an index to reference individual array elements. Either a number or a word can be an index. Number indices start with zero.

Arrays are named in exactly the same way as variables, but with square brackets after the array name. In the following example, words "cake," "bread," and "carrot" are added to an array.

$goods[]= "cake";
$goods[]= "bread";
$goods[]= "carrot";

A particular array element is referenced by specifying its index in square brackets. For example, the following code displays the contents of the zero element, which is "cake":

Error Handling in PHP

At certain configuration settings, PHP may not issue error messages. For production web sites, I recommend to keep this feature disabled. An extra message for a hacker is an extra hint to a successful break-in. For example, a message informing of excessive parameters tells me that the script does not check for the number of parameter passed to it, so it may not do other checks either, for example, whether the system function is called the right way. We will talk about the dangers inherent to this function repeatedly in this book.

A system used for application development must issue messages for any errors; otherwise, it is more likely than not that you will miss some potential errors, and will not be able to understand why the script code is not performing the way you intend it to.

The error reporting feature is enabled by setting the error_reporting parameter in the php.ini file to E_ALL. Error messages may be issued when numerical data is compared with string data. For example, adding a command error_reporting (E_ALL) command at the beginning of the script in which we considered the print_max() function (see Section 2.8) will produce the following error when a number and string are compared: