Clien authentication failed

[acuz]

[PHP] I followed step by step the Smart Buttons Integration and installed the SDK. placed my client Id on the client side (SANDBOX)

    <script src="https://www.paypal.com/sdk/js?client-id=<my clienT id here>"></script>

and placed my clientid and secret in the sdk file 

     $clientId = getenv("CLIENT_ID") ?: "<MY CLIENT ID>";

      $clientSecret = getenv("CLIENT_SECRET") ?: "MY CLIENT SECRET";

and copy pasted the php code for server side ; https://developer.paypal.com/docs/checkout/integrate/#6-verify-the-transaction

but when i print the promise ;

  onApprove: function(data, actions) {

                return actions.order.capture().then(function(details) {

                    alert('Transaction completed by ' + details.payer.name.given_name);

                    // Call your server to save the transaction

                    return fetch('paypal-transaction-complete.php', {

                        method: 'post',

                        headers: {

                            'content-type': 'application/json'

                        },

                        body: JSON.stringify({

                            orderID: data.orderID

                        })

                    }).then(function(res){

                        console.log(res.text());  //HERE I PRINT PROMISE IN CONSOLE

                    });

                });

            }

i get this error : Fatal error: Uncaught exception 'PayPalHttp\HttpException' with message '{"error":"invalid_client","error_description":"Client Authentication failed"}

Isnt the SDK supposed to deal with the authentication ? I'm stuck please help ! 

[MTS_Jennifer]

Hello,

Thank you for posting to the PayPal Merchant Technical Support Community.

You may want to do a var dump to see if your correct credentials are being passed in. If the credentials are not being passed in correctly then you will receive the Client Authentication Failed message. Also verify that you are not storing your credentials with a space before or after. A space will be seen as a character and can cause Client Authentication Failed message.

Thank you,

Jennifer

PayPal