title: Arduino joining string and *char
body: <p>I'm new to arduino and I have stumbled upon a problem. I want to send data via my esp8266 to my php page. But I don't know how to join my data with this GET request.</p>
  
  <p>Here is my code:</p>
  
  <pre class="lang-c prettyprint-override"><code>String card = "2-3d-fg-d6-12-68-32-3f-35-45-42-53-2a-3";
  char *hello = "GET /insert.php?card="+card+"&amp;error=1 HTTP/1.1\r\nHost: testsite.com\r\n\r\n"; 
  wifi.send((const uint8_t*)hello, strlen(hello));
  </code></pre>
  
  <p>And this is what I get in arduino console:</p>
  
  <blockquote>
    <p>error: cannot convert 'StringSumHelper' to 'char*' in initialization
    cannot convert 'StringSumHelper' to 'char*' in initialization</p>
  </blockquote>