PHP Variables

Introduction to PHP Variables

In PHP, variables are used to store data that can be used and manipulated throughout your script. Variables start with a dollar sign ($) followed by the variable name. The variable name must start with a letter or underscore, followed by any number of letters, numbers, or underscores.

Declaring Variables

<?php
$variableName = "value";
?>

Data Types

• String: Text data (e.g., $name = "John Doe";)
• Integer: Whole numbers (e.g., $age = 30;)
• Float: Decimal numbers (e.g., $price = 19.99;)
• Boolean: True or false (e.g., $isActive = true;)
• Array: Collection of values (e.g., $colors = array("red", "green", "blue");)
• Object: Instance of a class (e.g., $person = new Person("John");)
• NULL: No value (e.g., $emptyVar = null;)

Variable Scope

PHP variables have different scopes:

• Local: Variables declared inside a function or method.
• Global: Variables declared outside functions. To access global variables inside a function, use the global keyword or the $GLOBALS superglobal array.

Variable Variables

PHP supports variable variables, where you can use the value of one variable as the name of another variable.

<?php
$name = "world";
$$name = "Hello, world!";
echo $world; // Outputs: Hello, world!
?>

Type Casting

You can explicitly convert variables to a different data type.

<?php
$number = "42";
$integer = (int)$number;
?>