PHP TinyMce编辑器只保存部分发布的文本

Question

I created a PHP page containing a tinymce editor(WYSIWYG). This is used to update a single value in a database. On my development machine it works fine, however when in production it only saves a part of the text or nothing at all.

PHP CODE:

<form method="post">
            <div class="form-group">
                  <?php
                  if(!empty($_POST))
                  {
                      $param = "{$_POST['editor']}";
                      echo "<script> alertify.alert('{$param}'); </script>";
                      //echo '<script> alertify.notify("Opslaan geslaagd", "success"); </script>';

                      if(($stmt = $mysqli->query("UPDATE help SET _value = '{$param}' WHERE id = 1")))
                      {
                          echo '<script> alertify.notify("Opslaan geslaagd", "success"); </script>';
                      }
                      else
                      {
                          echo $mysqli->error;
                      }
                  }
                  ?>
                <textarea class="editor" name="editor" id="editor">
                    <?php 
                    if($result = $mysqli->query("SELECT _value FROM help WHERE id=1"))
                    {
                       $row = $result->fetch_assoc();
                       echo $row['_value'];
                    }?>
                </textarea>                   

                </div>
                <button type="submit" class="btn btn-primary">Opslaan</button>
        </form>

MYSQL STRUCTURE: mysql structure

PHP VERSION DEVELOPMENT: 5.6

PHP VERSION PRODUCTION: 5.5.2.3

Anybody knows what the problem is, and how I can solve it?