Private properties are not visible.

<?php
// cf. http://stackoverflow.com/questions/40230045/why-should-i-declare-the-class-property-in-php
class account {
    private $username;
    private $password;
    public function __construct($username, $password) {
        $this->username = $username;
        $this->password = $password;
    }
    public function getPassword() {
        return str_repeat('*', strlen($this->password));
    }
}

$a = new account('brandizzi', 'MySecretPassword');

echo $a->getPassword() . "\n";
echo $a->password . "\n";