PHP Variables: Declaration, Scope, and Data Types

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PHP Variables: Declaration, Scope, and Data Types
1. Declaring Variables in PHP
In PHP, variables start with a $ sign.

Variable names are case-sensitive ($name and $Name are different).

Variables do not need explicit type declarations (PHP is loosely typed).

✅ Example:

<?php

$name = "John";  // String

$age = 25;       // Integer

$price = 9.99;   // Float

$isAdmin = true; // Boolean

?>

2. PHP Variable Scope
Variable scope defines where a variable can be accessed in a script.

Types of Variable Scope:

Scope Description

Local Declared inside a function and accessible only within that function.

Global Declared outside a function and accessible throughout the script.

Static Retains its value even after the function exits.

Superglobal Special variables accessible anywhere (e.g., $_GET, $_POST).

Examples of Scope:

🔹 Local Variable Example

<?php

function myFunction() {

    $localVar = "I'm local!";

    echo $localVar;

}

myFunction();

// echo $localVar; // ❌ Error: Undefined variable

?>

🔹 Global Variable Example

<?php

$globalVar = "I'm global!";



function showVar() {

    global $globalVar; // Using 'global' to access outside variable

    echo $globalVar;

}

showVar();

?>

 

🔹 Static Variable Example

<?php

function counter() {

    static $count = 0; // Retains value across function calls

    $count++;

    echo $count . "
";

}



counter(); // Output: 1

counter(); // Output: 2

counter(); // Output: 3

?>

3. PHP Data Types
PHP supports different data types:

Data Type Example Description

String "Hello, PHP" A sequence of characters.

Integer 42 Whole numbers (positive or negative).

Float 3.14 Numbers with decimal points.

Boolean true or false Represents truth values.

Array ["Apple", "Banana", "Cherry"] Stores multiple values.

Object new ClassName() Represents an instance of a class.

NULL NULL Represents a variable with no value.

4. Data Type Examples
🔹 Strings

<?php

$text = "Hello, PHP!";

echo $text;

?>

🔹 Integers

<?php

$number = 100;

var_dump($number); // Output: int(100)

?> 

🔹 Floats

<?php

$pi = 3.14159;

var_dump($pi); // Output: float(3.14159)

?>

🔹 Booleans

<?php

$isPHPFun = true;

var_dump($isPHPFun); // Output: bool(true)

?> 

🔹 Arrays

<?php

$fruits = ["Apple", "Banana", "Cherry"];

echo $fruits[0]; // Output: Apple

?>

🔹 Objects

<?php

class Car {

    public $brand;

    function setBrand($brand) {

        $this->brand = $brand;

    }

}



$myCar = new Car();

$myCar->setBrand("Toyota");

echo $myCar->brand; // Output: Toyota

?>



🔹 NULL



<?php

$emptyVar = NULL;

var_dump($emptyVar); // Output: NULL

?>

Conclusion
PHP automatically assigns a data type based on the value.

Understanding scope helps avoid variable conflicts.

Arrays and Objects allow storing multiple values effectively.

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    Date: 2025-03-28 00:00:00.000000