A brief explannation of Callables and Closures.

closure_callable.php

<?php
// An Anonymous Class or Normal Classes
$class = new class {
    public function method() {
        echo 'In a Class!', PHP_EOL;
    }
};

// We can write this ... 🤔
$arrayLikeCallable = [new $class, 'method'];

/**
 * An array of 2 Elements whose 1st element is an object
 * and the second element is a public method that exists in that object ... is a Callable 🤭
 */
var_dump(is_callable($arrayLikeCallable)); // TRUE
// ... But it's not a Closure 🥶
var_dump($arrayLikeCallable instanceof Closure); // FALSE

// We can Convert Array based Callable to Closure Like this 😌
$closure = Closure::fromCallable($arrayLikeCallable);
// Then it becomes a closure 🤙✅
var_dump( $closure instanceof Closure); // TRUE

// This is an Anonymous function 👛
$function = function() {
    echo 'In a Function!', PHP_EOL;
};

// An Anonymous function is callable
var_dump(is_callable($function)); // TRUE
// An Anon function is also a Closure at the same time 👀
var_dump($function instanceof Closure); // TRUE



$class = new class {
    public function method() {
        echo 'In a Class!', PHP_EOL;
    }
};

$function = function() {
    echo 'In a Function!', PHP_EOL;
};

function callCallable(callable $callable) {
    call_user_func($callable);
}

$arrayLikeCallable = [new $class, 'method'];

callCallable($arrayLikeCallable);
callCallable($function);