grocery crud rename filename on upload - codeigniter

Question

I need to rename the file on file upload and inserting to the database.
I search for ways but i can't find the right code.
I tried to use callback but it did not work.
Here's my code:
public function home()
{
$crud = new grocery_CRUD();
$crud->set_theme('datatables');
$crud->set_table('blog_post');
$crud->set_field_upload('post_image',UPLOAD_PATH);
$crud->callback_before_upload(array($this,'_before_upload'))
$crud->callback_before_insert(array($this,'rename_img_db'));
$output = $crud->render();
$this->_example_output($output);
}
function rename_img_db($post_array)
{
if (!empty($post_array['post_image'])) {
$ext = end(explode(".",$post_array['post_image']));
$img_name = $post_array['post_image'] = mktime().".".$ext;
$post_array['post_image'] = $img_name;
}
return $post_array;
}
function _before_upload($files_to_upload,$field_info)
{
foreach($files_to_upload as $value) {
$ext = pathinfo($value['name'], PATHINFO_EXTENSION);
$rename = $value['name'];
}
$allowed_formats = array("jpg","gif","png","doc","docx","pdf");
if(in_array($ext,$allowed_formats))
{
return true;
}
else
{
return 'Wrong file format';
}
if ($rename) {
$ext1 = end(explode(".",$rename));
$img_name = $rename = mktime().".".$ext1;
$rename = $img_name;
return $rename;
}
}

Answer 1

I noticed a tipo in your line: $crud->callback_before_upload(array($this,'_before_upload'))
Moreover I had to do something similar and I used the callback_after_insert, then you can get the $primary_key variable and with that update the element, something like this:
$crud->callback_after_insert(array($this, 'rename_img_db'));
public function rename_img_db($post_array,$primary_key)
{
//Here goes the get and set querys with your $primary_key
}