HTML Forms (GET and POST) When a form is submitted to a PHP script, any variables from that form will be automatically made available to the script by PHP. For instance, consider the following form: Example 7-1. Simple form variable <form action="foo.php3" method="post"> Name: <input type="text" name="name"><br> <input type="submit"> </form> When

Sometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically. A normal variable is set with a statement such as: $a = "hello"; A variable variable takes the value of a variable and treats that as the name of a variable. In the above example, hello, can be used as the name of a variable by using

The scope of a variable is the context within which it is defined. For the most part all PHP variables only have a single scope. This single scope spans included and required files as well. For example: $a = 1; include "b.inc"; Here the $a variable will be available within the included b.inc script. However, within user-defined functions a local function scope is introduced.

PHP provides a large number of predefined variables to any script which it runs. Many of these variables, however, cannot be fully documented as they are dependent upon which server is running, the version and setup of the server, and other factors. Some of these variables will not be available when PHP is run on the command-line. Despite these factors, here is a list of predefined

Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive. Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: ‘[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*’ Note: