未定义的变量ajax

Question

This problem is kind of a bug. I don't know the problem in this code.
I'm using ajax to display the my table. and it said undefined variable: output.
Heres my code :

Controller Accounts:

function get_accounts()
{
    $accounts=$this->Model_admindly->get_accounts();
    $output.= '
      <table id="example" class="table table-striped table-bordered" cellspacing="0" width="100%">
              <thead>
                  <tr>
                      <th>ID</th>
                      <th>Email</th>
                      <th>Username</th>
                      <th>Last Logged</th>
                      <th>Last IP</th>
                      <th>Date Reg</th>
                      <th>Status</th>
                      <th>Actions</th>
                  </tr>
              </thead>
              <tfoot>
                  <tr>
                      <th>ID</th>
                      <th>Email</th>
                      <th>Username</th>
                      <th>Last Logged</th>
                      <th>Last IP</th>
                      <th>Date Reg</th>
                      <th>Status</th>
                      <th>Actions</th>
                  </tr>
              </tfoot>
              <tbody>';
    foreach($accounts as $key)
    {
        $output.= '<td>'.$key->id.'</td>
                     <td>'.$key->email.'</td>
                     <td>'.$key->username.'</td>
                     <td>'.$key->date_lastlogged.'</td>
                     <td>'.$key->last_ipaddress.'</td>
                     <td>'.$key->date_registered.'</td>
                     <td>'.$key->status.'</td>
                     <td>'.$key->status.'</td>';
    }
    $output.='</table>';
    echo $output;
}

To display it using ajax:

<script>
  $(document).ready(function(){
    function fetch_data()
    {
       $.ajax({
        url:"<?php echo base_url()?>Accounts/get_accounts",
        method:"POST",
        success:function(data)
        {
          $("#live_data").html(data);
        }
       });
    }
    fetch_data();
  });
</script>

Answer 1

You never initialized $output before you tried to .= it.

Essentially you have

$output = $output . 'foo';
              ^---undefined at this point

causing the error. You need to have

$output = ''; // create/initialize
$output .= 'foo'; // use