使用PHP curl调用webservice

I'm currently trying to call a POST web service with the PHP curl. I tried this, but without success (I receive "false", the objective is to receive a string from my web-service):

function devis( $data){
    $typeDevis = $data['typeDevis'];
    $compo = $data['compo'];
    $offre = $data['offre'];

    $url = "https://someadress:port/apiname/api/Devis";
    try{
        $fields = array(
            'typeDevis' => $typeDevis,
            'compo' => $compo,
            'offre' => $offre,
        );

        $fields_string = http_build_query($fields);

        $ch = curl_init();

        curl_setopt($ch,CURLOPT_URL, $url);
        curl_setopt($ch,CURLOPT_POST, count($fields));
        curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);

        $result = curl_exec($ch);

        curl_close($ch);
        return $result;
    }catch (Exception $e) {
        return $e;
    }
}

The link that must be called in POST is for example:

https://someadress:port/apiname/api/Devis?typeDevis=VALUE1&compo=VALUE2&offre=VALUE3

Does anyone have any ideas?

You need to modify your function as following:

function devis($data){
    $typeDevis = $data['typeDevis'];
    $compo = $data['compo'];
    $offre = $data['offre'];

    $url = "https://someadress:port/apiname/api/Devis";
    try{
        $fields = array(
            'typeDevis' => $typeDevis,
            'compo' => $compo,
            'offre' => $offre,
        );

        // You don't need to use this
        //$fields_string = http_build_query($fields);

        $ch = curl_init();

        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $fields);
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

        $result = curl_exec($ch);

        curl_close($ch);
        return $result;
    }catch (Exception $e) {
        return $e;
    }
}

Try to use proper curl syntax and be specific what you want to implement.
Also it would be better if you'll provide a proper header to your API request.