title: Checkbox always "on" when sending to php
body: <p>I have this checkbox in my html</p>
  
  <pre><code>&lt;input name="cb" class="cmn-toggle cmn-toggle-round" type="checkbox"&gt;
  </code></pre>
  
  <p>What I understood about how checkbox worked, was that when "checked" if you isset the input then it would "exist", and if wasn't "checked" wouldn't, so I did this:</p>
  
  <pre><code>if(isset($_REQUEST['cb'])){
     //do something
  }else{
    //do something else
  }
  </code></pre>
  
  <p>The problem is that when sending the form, it always exist, doesn't matter if checked or not, I don't know how to really see if really checked, so what am I doing wrong?</p>