从PHP中的cURL请求获取Foursquare access_token

Question

I'm testing a cURL function to get back the access token for a given user on Foursquare. The following function prints to the screen the access token in a json format

{"access_token":"5B25GW5LF3L4W04PALHK32X5Z3YGNUUVDHM2TFBQOWZSQ121"} 

I'm having problems in extracting the value of the access token.

This is the function I'm using:

function get_access_token($code){

        $url = "https://foursquare.com/oauth2/access_token";

        $fields = array(
            'client_id' => urlencode($this->client_id),
            'client_secret' => urlencode($this->client_secret),
            'grant_type' => 'authorization_code',
            'redirect_uri' => urlencode($this->redirect_url),
            'code' => $code
        );

        //url-ify the data for the POST
        foreach($fields as $key=>$value) { $fields_string .= $key.'='.$value.'&'; }
        rtrim($fields_string, '&');

        //open connection
        $ch = curl_init();

        //set the url, number of POST vars, POST data
        curl_setopt($ch,CURLOPT_URL, $url);
        curl_setopt($ch,CURLOPT_POST, count($fields));
        curl_setopt($ch,CURLOPT_POSTFIELDS, $fields_string);

        //execute post
        $result = curl_exec($ch);
        //close connection
        curl_close($ch);

        return var_dump($result) /* prints bool(true) */;
    }

How to I store this access token in a variable?

Thank you

Answer 1

By default curl_exec does not return the response, but a value indicating success or failure. Visit http://php.net/manual/en/function.curl-exec.php for more information.

Answer 2

Just add one more line of code to tell curl to pass the return value back to curl_exec and to your $result variable:

curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

You may also want to check if an error occurred when the data comes back: For example:

$result = curl_exec($ch);
if (curl_errno($ch)) 
   echo (curl_error($ch));
else
   echo $result;
curl_close($ch);