title: HTTPOISON - insert body parameters in elixir
body: <p>I'm trying to do a http request</p>
  
  <pre><code>def getPage() do
      url = "http://myurl"
      body = '{
                "call": "MyCall",
                "app_key": "3347249693",
                "param": [
                    {
                        "page"          : 1,
                        "registres"     : 100,
                        "filter"        : "N"
                    }
                ]
               }'
  
      headers = [{"Content-type", "application/json"}]
      HTTPoison.post(url, body, headers, [])
  end
  </code></pre>
  
  <p>this works for me well. </p>
  
  <p>my question is - how can I insert variables in the body request.
  meaning:</p>
  
  <pre><code> def getPage(key, page, registers, filter) do
      url = "http://myurl"
      body = '{
                "call": "MyCall",
                "app_key": key,
                "param": [
                    {
                        "page"          : page,
                        "registres"     : registers,
                        "filter"        : filter
                    }
                ]
               }'
  
      headers = [{"Content-type", "application/json"}]
      HTTPoison.post(url, body, headers, [])
  end
  </code></pre>
  
  <p>when I run it I get   </p>
  
  <pre><code>%HTTPoison.Response{body: "\nFatal error: Uncaught exception 'Exception' with message 'Invalid JSON object' in /myurl/www/myurl_app/api/lib/php-wsdl/class.phpwsdl.servers.php:...
  </code></pre>
  
  <p>any suggestions?</p>