title: how to divide a string, I mean convert 0123456789 into "01","12","23","34","45","56","67","78","89"
body: <p>I want to know how to split numbers, such as we fill 0123456789 data as the processing.
  I want the results to come out.
   "01","12","23","34","45","56","67","78","89" 
  I found the problem is Bad Request (#400)
  Unable to verify your data submission.
  mycontroller</p>
  
  <pre><code>public function actionAbout() {
      $datas = yii::$app-&gt;request-&gt;post();
      $n = isset($datas['n']) ? $datas['n'] : NULL;
      $m = $n;
  
  
      return $this-&gt;render('about', [
                  'n' =&gt; $n,
                  'm' =&gt; $m,
      ]);
  }
  </code></pre>
  
  <p>view</p>
  
  <pre><code>&lt;form method="POST"&gt;
  &lt;div class="col-md-2"&gt;
      &lt;?php echo Html::textInput('n', $n); ?&gt;
  &lt;/div&gt;
  &lt;button class='btn-danger btn-md'&gt;ตกลง &amp;raquo;&lt;/button&gt;
  </code></pre>
  
  <p></p>
  
  <pre><code>&lt;?php
  $data = $m;
  $substr = null;
  for ($i = 0; $i &lt; strlen($data) - 1; $i++) {
      $substr = substr($data, $i, 2);
      echo $substr . ", ";}?&gt;
  </code></pre>