Is it possible to create static classes in PHP (like in C#)?


Question

I want to create a static class in PHP and have it behave like it does in C#, so

  1. Constructor is automatically called on the first call to the class
  2. No instantiation required

Something of this sort...

static class Hello {
    private static $greeting = 'Hello';

    private __construct() {
        $greeting .= ' There!';
    }

    public static greet(){
        echo $greeting;
    }
}

Hello::greet(); // Hello There!
1
134
1/22/2009 10:30:57 AM

Accepted Answer

You can have static classes in PHP but they don't call the constructor automatically (if you try and call self::__construct() you'll get an error).

Therefore you'd have to create an initialize() function and call it in each method:

<?php

class Hello
{
    private static $greeting = 'Hello';
    private static $initialized = false;

    private static function initialize()
    {
        if (self::$initialized)
            return;

        self::$greeting .= ' There!';
        self::$initialized = true;
    }

    public static function greet()
    {
        self::initialize();
        echo self::$greeting;
    }
}

Hello::greet(); // Hello There!


?>
195
11/23/2016 11:23:51 PM

In addition to Greg's answer, I would recommend to set the constructor private so that it is impossible to instantiate the class.

So in my humble opinion this is a more complete example based on Greg's one:

<?php

class Hello
{
    /**
     * Construct won't be called inside this class and is uncallable from
     * the outside. This prevents instantiating this class.
     * This is by purpose, because we want a static class.
     */
    private function __construct() {}
    private static $greeting = 'Hello';
    private static $initialized = false;

    private static function initialize()
    {
        if (self::$initialized)
            return;

        self::$greeting .= ' There!';
        self::$initialized = true;
    }

    public static function greet()
    {
        self::initialize();
        echo self::$greeting;
    }
}

Hello::greet(); // Hello There!


?>

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