title: PHP implode(): Invalid arguments passed
body: <p>I have a php form which has a checkbox option in which if the user selects 'Other', a text input appears. This is working well but the data is not submitting. Im gettting the error message <strong>PHP implode(): Invalid arguments passed</strong> </p>
  
  <p>Here is: </p>
  
  <p>PHP validation</p>
  
  <pre><code>if(!isset($_POST['competitor_model'])){   
  echo '&lt;p&gt;&lt;font color="red" size="+1"&gt;• Please select at least one competitor model&lt;/font&gt;&lt;/p&gt;';
  } else {
  $compmodel = implode(',', $_POST['competitor_model']); 
  }
  </code></pre>
  
  <p>Here is the JS/HTML form</p>
  
  <pre><code>        &lt;script type="text/javascript"&gt;
          var temp = '';
          function disableTxt() {
          var field = document.getElementById("other");
          if(field.value != '') {
          temp = field.value;
          }
          field.style.display = "none";
          field.value = '';
          }
          function enableTxt() {
          document.getElementById("other").style.display = "inline";
          document.getElementById("other").value = temp;
          }
          &lt;/script&gt;         
  
  
          &lt;input type="checkbox" value="BMW 3-series" onchange="disableTxt()"  name='competitor_model[]'&gt;BMW 3-series&lt;br&gt;
          &lt;input type="checkbox" value="Mercedes Benz C-class" onchange="disableTxt()"  name='competitor_model[]'&gt;Mercedes Benz C-class&lt;br&gt;
          &lt;input type="checkbox" value="Lexus IS" onchange="disableTxt()"  name='competitor_model[]'&gt;Lexus IS&lt;br&gt;
          &lt;input type="checkbox" value="Audi A4" onchange="disableTxt()" name='competitor_model[]'&gt;Audi A4&lt;br&gt;
          &lt;input type="checkbox" value="Other"  onchange="enableTxt(Number)" name='competitor_model[]'&gt;Other &lt;em&gt;If yes please submit model&lt;/em&gt;
          &lt;input type="text" name="competitor_model[]" id="other" style="display:none;" value="&lt;?php if (isset($_POST['competitor_model'])) echo $_POST['competitor_model']; ?&gt;"/&gt;
  </code></pre>