code/services/LDAPService.php
public function getUsernameByEmail($email)
    {
        $data = $this->getUserByEmail($email);
        if (empty($data)) {
            return null;
        }

        return $this->gateway->getCanonicalUsername($data);
    }
public function getUsernameByEmail($email)
    {
        $data = $this->getUserByEmail($email);
        if (empty($data)) {
            return null;
        }

        return $this->gateway->getCanonicalUsername($data);
    }
Get a username for an email.

@param string $email
@return string|null