IsThisSecure.php

<?php

class A {

    /**
     * @param $args
     */
    public function methodIsCool($args) {
        var_dump($args);
    }
}

$userRequest = $_GET['userRequest'] ?? null;
$method = $userRequest . 'IsCool';
$args = [];
$a = new A();
if (method_exists($a, $method)) {
    $a->$method($args);
} else {
    var_dump('err: ' . $method);
}