Response to "Store function expression to a variable in PHP inside a class" stackoverflow question

test-it.php

<?php

	class Demo
	{
		static public $var;
		public $a;
		public function __construct()
		{
			$this->a = function()
			{
				return 'hello there';
			};
		}
		public function a()
		{
			return 'hello world';
		}
	}

	// You can store information directly on the class via static
	// Otherwise anything else is stored in the instance of the class, not the class directly.
	Demo::$var = function(){ return 'hello internets'; };


	// Not sure if we're running via terminal/CLI/console or an HTML browser
	// So assume terminal, and make the browser accept raw text instead of HTML.
	header('Content-Type: text/plain');

	$x = new Demo;
	echo ($x->a)(); // hello there
	echo "\n";
	echo $x->a(); // hello world
	echo "\n";
	echo (Demo::$var)(); // hello internets
	
	// Just to show you this can all be assigned to a variable of its own and accessed as variables without parentheses
	list($a,$b,$c) = [$x->a, function() use($x){return call_user_func_array([$x,'a'],func_get_args());},Demo::$var];

	echo "\n\n";
	echo $a();
	echo "\n";
	echo $b();
	echo "\n";
	echo $c();

Run as either php -S localhost:8000 test-it.php or php test-it.php from your terminal.
If running the first way, access as http://localhost:8000/ in your browser.
Otherwise, the output will display directly in your terminal.