authentication.php
public function setIdentityForRealm($host, $realm, $username, $password)
    {
        if (isset($this->realms[$host][$realm])) {
            $this->realms[$host][$realm]->setIdentity($username, $password);
        }
    }
public function setIdentityForRealm($host, $realm, $username, $password)
    {
        if (isset($this->realms[$host][$realm])) {
            $this->realms[$host][$realm]->setIdentity($username, $password);
        }
    }
Sets the current identity to be presented against that realm.

@param string $host        Server hosting realm.
@param string $realm       Name of realm.
@param string $username    Username for realm.
@param string $password    Password for realm.