cannot load data from database, the result is blank screen

[eluser]Unknown[/eluser]
@Einstein
thanks you for your response. I also changed my code as your suggest (thanks for correction, I think mistyping code). but I still got blank screen. actualy, I don't know what happens???.

@seppo
I have activate my display_error, and I got error message why it cannot works like this
Parse error: syntax error, unexpected '=' in C:\apache2triad\htdocs\tutorial\system\application\models\display_model.php on line 20

I have revised my code, but it still not works. I don't know what wrong? I attach my screnshoot-code which write with italic to this post.

function Display_model()
{
parent::Model();
}

function SelectData()
{
$this->db->orderby('function_name');
$this->db->limit(10);
$query = $this->db->get('function');
if ($query->num_rows() > 0)
{
//$output = '<table>';
//$output. = '<tr><td>Function Name</td><td>Function Description</td></tr>';
foreach ($query->result() as $row)
{
$output = $row->function_name;
$output. = $row->function_description;
}
//$output. = '</table>';
return $output;
}
else
{
return '<p>Sorry, no results returned.</p>';
}

overall, thanks for kindly help. I hope you response my post-issue