Error access token with LinkedIn - php

Question

After many tests, I cannot retrieve the access token. It gives me every time this error:
"error_description":"missing required parameters, includes an invalid parameter value, parameter more than once. : Unable to retrieve access token : authorization code not found","error":"invalid_request"
I totally distraught. For a few days I cannot solve my problem.
Here is the code of my application :
Route::get('login/linkedin', function()
{
$lk_credentials = Config::get('linkedin.public0');
$provider = new LinkedIn($lk_credentials);
if(!Input::has('code')){
$provider->authorize();
}else{
$code = Input::get('code');
if(strlen($code) == 0) return Redirect::to('/')->with('message', 'There was an error communicating with LinkedIn');
try{
$params = array(
'response_type' => 'code',
'client_id' => '*************',
'redirect_uri' => urlencode(url('login/linkedin')),
'state' => $_GET['state'],
);
$postdata = http_build_query($params);
$url = '/uas/oauth2/authorization?'.$postdata;
$context = stream_context_create(array('https' => array('method' => 'GET')));
$t = $provider->getAccessToken('authorization_code', array('code' => $_GET['code']));
Session::put('oauth2_access_token', $t->accessToken);session(['oauth2_access_token' => $t->accessToken]);
try{
if(count($_POST) > 0){
print_r($_POST);
exit('post');
}
$params = array(
'grant_type' => 'authorization_code',
'code' => Session::get('oauth2_access_token'), //$_GET['code'],
'redirect_uri' => urlencode(url('login/linkedin')),
'client_id' => '123456789',
'client_secret' => '123456789',
);
$postdata = http_build_query($params);
$c = curl_init();
curl_setopt($c, CURLOPT_URL, 'https://www.linkedin.com/uas/oauth2/accessToken');
curl_setopt($c, CURLOPT_RETURNTRANSFER, true);
curl_setopt($c, CURLOPT_POST,true);
curl_setopt($c, CURLOPT_CUSTOMREQUEST, "POST");
curl_setopt($c, CURLOPT_POSTFIELDS,$postdata);
curl_setopt($c, CURLOPT_HEADER, false);
curl_setopt($c, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded',));
$output = curl_exec($c);
if($output === false){
trigger_error('Erreur curl : '.curl_error($c),E_USER_WARNING);
exit('Erreur');
}else{
var_dump($output);
//exit('Affiche');
}
curl_close($c);
}catch(Exception $e){
return 'Unable to get Request Token';
}
}catch(Exception $e){
return 'Unable to get user authorization_code';
}
try{
$resource = '/v1/people/~:(id,emailAddress,firstName,lastName,pictureUrl,dateOfBirth,location)';
$params = array(
'oauth2_access_token' => Session::get('oauth2_access_token'),
'format' => 'json',
);
$url = 'https://api.linkedin.com' . $resource . '?' . http_build_query($params);
$context = stream_context_create(array('http' => array('method' => 'GET')));
$response = file_get_contents($url, false, $context);
$data = json_decode($response);
Session::put('data', $data);session(['data' => $data]);
return redirect('/')->with('data',$data);
}catch(Exception $e){
return 'Unable to get user details';
}
}
});
Does anyone could help me?
For information; I use Laravel5 and for the authentication is OAuth2.
Thank you in advance, David.