test.php

<?php

// Just showing you: say nonexistent had defined a variable called $foo that is a boolean, we can hint that too
include 'nonexistent.php';

/** @var bool $foo */
if($foo) {  // this won't say undefined variable in the editor!
    echo "foo was true in nonexistent.php";
}

class x {
    /**
     * @return array
     */
    public function getContainer() {
        return [];
    }

    /**
     * Returns true if a user exists with the given username or email, false otherwise
     *
     * @param string $username     The username
     * @param string $email        The email address
     *
     * @return boolean            If a user exists with given username or email address.
     */
    public function exists($username, $email){
        /**
         * @var PDO $db
         */
        $db = $this->getContainer()['db'];
        $stmt = $db->prepare("SELECT COUNT(*) AS count FROM userprofile WHERE username = :username OR email = :email");
        $stmt->execute(array(':name'=>$username, ':email'=>$email));
        $results = $stmt->fetch(\PDO::FETCH_ASSOC);

        // Let's pretend that $results was an array of Iterators
        // as in the built in "iterator" class: http://us1.php.net/manual/en/class.iterator.php
        // you can even hint at $x in the loop's scope

        foreach($results as $x) {
            /** @var Iterator $x */
            $x->


        }

        #return (int) $results['count'] > 0 ? true : false;

        echo $username, $email, "\n";

        return true;
    }
}

$x = new x();
$x->exists("username", "email");