Variables and Datatypes in PHP

A variable in PHP is a container used to store data. The value of a variable can change during program execution. PHP variables start with a dollar sign ($), followed by the variable name.

$name = "GFG";
$age = 30;

Declaring Variables in PHP

To declare a variable, you simply use the dollar sign followed by the variable's name and assign it a value.

$variableName = "value";

Rules for Naming Variables

There are a few rules when naming variables in PHP:

• Variable names must start with a dollar sign ($), followed by a letter or an underscore.
• The rest of the variable name can contain letters, numbers, and underscores.
• Variable names are case-sensitive.
• For example, $name and $Name are different variables.

Variable Scope

PHP variables have different scopes depending on where they are declared:

• Global scope: Variables declared outside of functions are accessible throughout the script.
• Local scope: Variables declared inside a function are only accessible within that function.
• Static scope: Variables declared as static within a function retain their value across multiple function calls.

//Driver Code Starts
<?php
//Driver Code Ends

  $globalVar = "I am global";

  function test() {
    $localVar = "I am local";
    echo $globalVar;  // This will cause an error because $globalVar is not in the local scope
  }

  test();

//Driver Code Starts
?>

//Driver Code Ends

For more details read the article – PHP Variables

Datatype in PHP

In PHP, data types refer to the type of data a variable can hold. PHP supports several data types, including scalar types (integers, floats, booleans, and strings) and compound types (arrays and objects).

1. String

A string is a sequence of characters enclosed in either single quotes (') or double quotes ("). Strings can store text or a combination of text and numbers.

<?php
  $name = "Anjali"; // String with double quotes
  $greeting = 'Hello, World!'; // String with single quotes
?>

2. Integer

An integer is a whole number without a decimal point. It can be positive or negative. PHP supports both decimal and octal numbers.

<?php
  $age = 30;     // Decimal integer
  $negative = -10;  // Negative integer
?>

3. Float (Double)

A float (also known as a double or real number) is a number with a decimal point.

<?php
  $price = 19.99;    // Float
  $temperature = -5.5;  // Negative float
?>

4. Boolean

A boolean represents two possible values: true or false. It is used in logical operations and control structures.

<?php
  $isStudent = true;  // Boolean value true
  $isAdult = false;   // Boolean value false
?>

5. Array

An array is a collection of values stored in a single variable. PHP supports both indexed arrays (numeric keys) and associative arrays (string keys).

<?php
  // Indexed array
  $colors = array("red", "green", "blue");
  // Associative array
  $person = array("name" => "Anjali", "age" => 25);
?>

6. Object

An object is an instance of a class. Objects can hold both data and methods to manipulate that data. PHP is an object-oriented language, and objects are central to working with classes.

<?php
  class Person {
    public $name;
    public $age;

    function __construct($name, $age) {
      $this->name = $name;
      $this->age = $age;
    }

    function greet() {
      return "Hello, " . $this->name;
    }
  }

  $person1 = new Person("Anjali", 30);
  echo $person1->greet(); // Output: Hello, Anjali
?>

7. NULL

The NULL data type represents a variable with no value assigned. A variable is considered NULL if it has been explicitly set to NULL or if it has not been initialized.

<?php
  $emptyVar = NULL;  // Variable with NULL value
?>

For more details read the article – PHP Data types