$url = 'http://www.webservicex.net/airport.asmx/GetAirportInformationByCountry';
                    $ch = curl_init();
                    curl_setopt($ch, CURLOPT_URL, $url);
                    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
                    curl_setopt($ch, CURLOPT_POST, 1);
                    curl_setopt($ch, CURLOPT_POSTFIELDS, 'country=paramAero');
                    curl_setopt($ch, CURLOPT_HEADER, 0);
                    curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
                    $result = curl_exec($ch);
                    $err = curl_error($ch);
                curl_close($ch);

                    $result = substr($result, 114);
                $result = substr($result,0,- 30);
                $result = chop($result);
                $borra = array("Table","CityOrAirportName","<",">","/");
                $output = str_replace($borra, '',$result);
                $output = explode(PHP_EOL, $output);

            $xml = simplexml_load_string($xml);


            $i=0;
                $aero = array();
                foreach ($output as $value) {
                    if(strlen($value)>3){
                        $aero[++$i] = $value;
                    }
                }
                echo '<select id="campoAeropuerto" name="campoAeropuerto">';

                foreach($aero as $key => $value){
                    echo '<option value="'.$key.'">'.$value.'</option>';
                }
                echo '</select>';