Learn static methods, static properties, utility classes, and the Singleton pattern.

Static Properties and Methods

Static members belong to the class itself, not an object.

class Counter
{
    public static int $count = 0;

    public static function increment()
    {
        self::$count++;
    }
}

Counter::increment();
Counter::increment();

echo Counter::$count; // 2

Use Cases

• Counters
• Configuration values
• Utility functions
• Shared data

Static Utility Class

A class containing only static methods.

class StringHelper
{
    public static function slug(string $text): string
    {
        return strtolower(str_replace(' ', '-', $text));
    }

    public static function upper(string $text): string
    {
        return strtoupper($text);
    }
}

echo StringHelper::slug("Hello World");
// hello-world

Benefits

• No object creation needed
• Easy reusable helper functions

Singleton Pattern

Ensures only one instance of a class exists.

class Database
{
    private static ?Database $instance = null;

    private function __construct()
    {
        echo "Connected";
    }

    public static function getInstance(): Database
    {
        if (self::$instance === null) {
            self::$instance = new Database();
        }

        return self::$instance;
    }
}

$db1 = Database::getInstance();
$db2 = Database::getInstance();

var_dump($db1 === $db2); // true

Comparison