Variables and Data Types

One of the first things to understand when learning any programming language are variables and data types.

Variables

In PHP, variables are declared with a dollar sign $ followed by the variable's name. PHP is a loosely typed language, which means that you don't have to declare the data type of a variable when you create one. Here's an example:

<?php
$name = "Alice"; // This is a string.
$age = 25; // This is an integer.
$weight = 65.5; // This is a float.
$isStudent = true; // This is a boolean.
?>

Data Types

PHP supports several data types, which define what kind of data a variable can hold:

1. String: A sequence of characters, like "Hello, World!". Strings are defined by enclosing the text in quotes:

   <?php
   $string = "Hello, World!";
   echo $string; // Outputs: Hello, World!
   ?>

2. Integer: A non-decimal number. Integers can be positive or negative:

   <?php
   $integer = 42;
   echo $integer; // Outputs: 42
   ?>

3. Float (or double): A number with a decimal point or a number in exponential form:

   <?php
   $float = 3.14;
   echo $float; // Outputs: 3.14
   ?>

4. Boolean: Represents two possible states: TRUE or FALSE:

   <?php
   $boolean = true;
   echo $boolean; // Outputs: 1 (for TRUE)
   ?>

5. Array: An ordered map (a type of data structure that pairs keys with values):

   <?php
   $array = array("Alice", "Bob", "Charlie");
   print_r($array); // Outputs: Array ( [0] => Alice [1] => Bob [2] => Charlie )
   ?>

6. Object: Instances of classes, which PHP allows you to create so that you can use objects to manage and organize your code (discussed in detail in a later section):

   <?php
   class Car {
       function Car() {
           $this->model = "VW";
       }
   }
   $herbie = new Car(); // create an object
   echo $herbie->model; // show object properties
   ?>

7. NULL: A special data type representing a variable with no value. A variable of data type NULL is a variable that has no value assigned to it:

   <?php
   $var = NULL;
   var_dump($var); // Outputs: NULL
   ?>