index not set (Undefined index) PHP $_POST

Question

Good guys am Android Dev, but I don’t know much about WEB, so I took an example of another Android Dev in which it uses an online "system" that displays a map and makes some entries but whenever I open the main page notice appears in php.

<?php
if(!isset($_SESSION)) 
{ 
    session_start(); 
} 
@include_once('conf/config.php');
@include_once(__PATH__.'/conf/config.php');
require_once(__PATH__.'/package/apl/AplMap.php');


if( preg_match('/^(get-map-content|get-form-create-place|get-form-update-place){1}$/', $_POST['method']) ){ 

    if(preg_match('/^(get-form-update-place){1}$/', $_POST['method'])){
        $apl = new AplMap();
        $arrayPlaces = $apl->getPlacesLightWeight();
    }

    header('Content-Type: text/html; charset=iso-8859-1');
    require_once(__PATH__.'view/content-location-api-app.php');
}


else if(preg_match('/^(send-map-coords){1}$/', $_POST['method'])
    || preg_match('/^(send-map-coords){1}$/', $_GET['method'])){

    $apl = new AplMap();
    $map = new Map();
    $map->post( $_POST );
    $return = $apl->saveMapCoord( $map );

    echo json_encode(array( 'feedback'=>$return ));
}


else if(preg_match('/^(get-last-map-coords){1}$/', $_POST['method'])
    || preg_match('/^(get-last-map-coords){1}$/', $_GET['method'])){
    $apl = new AplMap();
    $user = new User(1);
    $map = $apl->getLastMapCoord( $user );

    echo json_encode(array( 'map'=>is_null($map) ? '' : $map->getDataJSON() ));
}


else if(preg_match('/^(create-place){1}$/', $_POST['method'])){
    $apl = new AplMap();

    $place = new Place();
    $place->post( $_POST );
    $return = $apl->savePlace( $place );

    echo json_encode(array( 'feedback'=>$return ));
}


else if(preg_match('/^(update-place){1}$/', $_POST['method'])){
    $apl = new AplMap();

    $place = new Place( $_POST['id-place'] );
    $place->post( $_POST );
    $return = $apl->updatePlace( $place );

    echo json_encode(array( 'feedback'=>$return ));
}


else if(preg_match('/^(get-place-data){1}$/', $_POST['method'])){
    $apl = new AplMap();

    $place = new Place( $_POST['id-place'] );
    $place->post( $_POST );
    $place = $apl->getPlace( $place );

    echo json_encode(array( 'place'=>$place->getDataJSON() ));
}


else if(preg_match('/^(get-places-closest){1}$/', $_POST['method'])){
    $apl = new AplMap();

    $place = new Place();
    $place->setLatitude( $_POST['latitude'] );
    $place->setLongitude( $_POST['longitude'] );
    $place->setDistance( $_POST['distance'] );

    $arrayPlaces = $apl->getPlacesClosest( $place );


    // SEND TO CLIENT
        $tam = count($arrayPlaces);
        $arrayJson = array();

        for($i = 0; $i < $tam; $i++){
            $arrayJson[] = $arrayPlaces[$i]->getDataJSON();
        }

        $arrayJson = array('places'=>$arrayJson);
        echo json_encode($arrayJson);
}

?>