Portability

PHP is designed to run on many operating systems and to cooperate with many servers and databases. You can build for a Unix environment and shift your work to NT without a problem. You can test a project with Personal Web Server and install it on a Unix system running on PHP as an Apache module.

Variables

A variable is a special container you can define to hold a value. Variables are fundamental to programming.

A variable is a holder for a type of data. It can hold numbers, strings of characters, objects, arrays, or booleans. The contents of a variable can be changed at any time.

PHP is loosely typed, which means it calculates data types as data is assigned to each variable.

Six standard data types available in PHP.

          Type                                                              Example                                                  Description

            Integer                                                                                  5                                                                           A whole number

            Double                                                                             3.234                                   A floating-point number

            String                                                                              "hello"                                  A collection of characters

            Boolean                                                                           true                                    One of the special values true or false

           Object                                                                  class Item

                                                                                    { var $name = "item"; }

                                                                                     $obj1 = new Item();

                                                                                    $obj2 = new Item();

                                                                                   $obj1->name = "widget 5442";

                                                                                  print "$obj1->name<br />";

                                                                                 print "$obj2->name<br />";

                                          

           Array                                          $membertypes = array ("regular", "regular", "regular", $regular");                     "Arrays"

Special Data Types

                   Type                                                                                                                                                          Description

            Resource                                                                    Reference to a third-party resource (a database, for example)

            NULL                                                                         An uninitialized variable