PHP: Booleans, Arrays, Objects, Null, and Constants
PHP: Booleans, Arrays, Objects, Null, and Constants
1. Booleans
A Boolean in PHP represents true (1) or false (0). Booleans are often used in conditional statements.
✅ Example:
<?php
$isPHPFun = true;
$isJavaHard = false;
var_dump($isPHPFun); // Output: bool(true)
var_dump($isJavaHard); // Output: bool(false)
?>
✅ Booleans in Conditions:
<?php
$loggedIn = true;
if ($loggedIn) {
echo "Welcome, User!";
} else {
echo "Please log in.";
}
?>
2. Arrays
An array is a collection of values stored under a single variable. PHP supports three types:
Indexed Arrays (Numeric keys)
Associative Arrays (Named keys)
Multidimensional Arrays (Arrays inside arrays)
🔹 Indexed Arrays (Numeric Keys)
<?php
$fruits = ["Apple", "Banana", "Cherry"];
echo $fruits[0]; // Output: Apple
?>
🔹 Associative Arrays (Key-Value Pairs)
<?php
$person = ["name" => "John", "age" => 30];
echo $person["name"]; // Output: John
?>
🔹 Multidimensional Arrays
<?php
$students = [
["John", 25, "A"],
["Alice", 22, "B"],
];
echo $students[0][0]; // Output: John
?>
3. Objects
An object is an instance of a class. Objects allow data to be stored as properties and methods.
✅ Example:
<?php
class Car {
public $brand;
function setBrand($brand) {
$this->brand = $brand;
}
}
$myCar = new Car();
$myCar->setBrand("Toyota");
echo $myCar->brand; // Output: Toyota
?>
4. NULL in PHP
NULL is a special data type that represents a variable with no value.
A variable is NULL if it:
Has not been assigned a value.
Has been set to NULL.
Has been unset().
✅ Example:
<?php
$var = NULL;
var_dump($var); // Output: NULL
?>
5. PHP Constants
A constant is a value that cannot be changed during script execution.
Defined using define() or const.
✅ Using define() (Works in PHP 5.3+)
<?php
define("SITE_NAME", "MyWebsite");
echo SITE_NAME; // Output: MyWebsite
?>
✅ Using const (Works in PHP 5.6+)
<?php
const PI = 3.14159;
echo PI; // Output: 3.14159
?>
✅ Case Sensitivity
By default, constants are case-sensitive.
Use true as the third parameter in define() to make them case-insensitive.
<?php
define("GREETING", "Hello, World!", true);
echo greeting; // Output: Hello, World!
?>
Conclusion
Booleans are useful for logic (true or false).
Arrays store multiple values (indexed, associative, multidimensional).
Objects represent real-world entities with properties and methods.
NULL represents a variable with no value.
Constants store values that never change during execution.
Date: 2025-03-28 00:00:00.000000