invalid operands of types 'const char*' and 'const char [8]' to binary 'operator

Projects Programming
1 
if (camClient.connect(postHost, postHttpPort))
    {
      uint8_t num =12;
      String base64image =  "id=1234&num=" +  num + "&image=" + base64::encode(fb->buf, fb->len);
      
      Serial.println("connection");
      camClient.println("POST /test/image/post.php HTTP/1.0");
      camClient.println("Host: cloud.***.com");
      camClient.println("Accept: */*");
      camClient.println("User-Agent: Mozilla/5.0");
      camClient.println("Content-Length: " + (base64image.length());
      camClient.println("Content-Type: image/jpeg" );
      camClient.println();
      camClient.write(base64image.c_str());

      //Serial.println(base64_encode_expected_len(fb->len) + 1);
      
      camClient.stop();
    }
    else {
      // if you didn't get a connection to the server:
      Serial.println("connection failed");
    }

ERROR invalid operands of types 'const char*' and 'const char [8]' to binary 'operator+'

Help me to understand

2

You can't add an array to a string.

3

TheMemberFormerlyKnownAsAWOL:
You can't add an array to a string.

What should I do?

4

Print them separately?

5

TheMemberFormerlyKnownAsAWOL:
Print them separately?

yes if not difficult

6

TheMemberFormerlyKnownAsAWOL:
Print them separately?

Wrote and it works
String base64image = "id=1234&num=" +num + base64::encode(fb->buf, fb->len)+ "&image=";