title: Google reCAPTCHA: incorrect-captcha-sol error
body: <p><br>
  I'm having an issue using Google captcha in may php contact form.<br>
  I followed the Google official guide and the code I wrote seems to be correct but I receive always the <strong>incorrect-captcha-sol</strong> error.</p>
  
  <p>Client side code:</p>
  
  <pre><code>&lt;div class="row"&gt;
      &lt;div class="12u"&gt;
          &lt;form id="mailform" method="post" action="website_mailer.php" novalidate="novalidate"&gt;
              &lt;div&gt;
                  &lt;div class="row half"&gt;
                      &lt;div class="6u"&gt;
                          &lt;input type="text" name="name" id="name" placeholder="Name" /&gt;
                      &lt;/div&gt;
                      &lt;div class="6u"&gt;
                          &lt;input type="text" name="email" id="email" placeholder="Email" /&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="row half"&gt;
                      &lt;div class="12u"&gt;
                          &lt;input type="text" name="subject" id="subject" placeholder="Subject" /&gt;
                          &lt;input type="text" class="myantispam" name="leaveblank"&gt;
                          &lt;input type="text" class="myantispam" name="dontchange" value="http://" &gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="row half"&gt;
                      &lt;div class="12u"&gt;
                          &lt;textarea name="message" id="message" placeholder="Message"&gt;&lt;/textarea&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
                  &lt;div class="row half"&gt;
                      &lt;div class="4u"&gt;
                          &lt;div class="g-recaptcha" data-sitekey="xxxx"&gt;&lt;/div&gt;
                      &lt;/div&gt;
                      &lt;div class="8u"&gt;
                          &lt;a href="#" class="button form-button-submit"&gt;Send Message&lt;/a&gt;
                          &lt;a href="#" class="button button-alt form-button-reset"&gt;Clear Form&lt;/a&gt;
                      &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/form&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Server side code (PHP):</p>
  
  <pre><code>&lt;?php
  require_once('recaptchalib.php');
  
  $privatekey = "xxx";
  $resp = recaptcha_check_answer ($privatekey,
                                  $_SERVER["REMOTE_ADDR"],
                                  $_POST["recaptcha_challenge_field"],
                                  $_POST["recaptcha_response_field"]);
  
  if (!$resp-&gt;is_valid) {
          die ("The reCAPTCHA wasn't entered correctly. Go back and try it again." .
           "(reCAPTCHA said: " . $resp-&gt;error . ")");
      } else {
        /* proper code */
      }
  ?&gt;
  </code></pre>
  
  <p>Can you suggest me a solution? I'm not able to find a solution.</p>
  
  <p>Thanks!</p>