PHP return function

Although the variable url is returning content, according to VAR_DUMP, the code below exits the message "URL not existent". Why that? Where am I sinning in the code?

public function getUrlcliente($cliente_id) {

        $parametro = "cliente_id=" . (int)$cliente_id;
        $url_externa = $this->db->query("SELECT DISTINCT query as indice, keyword as url FROM url_alias WHERE query = '" . $parametro . "'");

        if (empty($url_externa)) {
            $url = "Erro - URL amigável não cadastrada";
        }
        else {
            foreach ($url_externa as $row) {
                var_dump($row);
                if (isset($row->url)) {
                    $pos = strpos($row->url, "www");
                    if ($pos == false) {
                    }
                    else {
                        $url = $row->url;
                        break;
                    }
                }
                else {
                    $url = "Url inexistente";  ---> ele está saindo aqui
                }
            }
        }

        if ($url_externa->num_rows) {
                    return $url;
                }
        else
                {
                    return "Erro-Url inexistente";
                }
}

VAR_DUMP is returning this ---- >

  

int (1) array (2) {["index"] = > string (13) "client_id = 42" ["url"] = > string (21) " link "} array (1) {[0] = > array (2) {["index"] = > string (13) "client_id = 42" ["url"] = > string (21) " link "}}

Note that the purpose of the function is to return only one string, the URL, I do not want it to return an array.