Stop user from deleting a set file name not working

I have a file in two locations called no_image.jpg When user try's to delete the image I would like to be able to stop the user from deleting just that image.

But for some reason the image still gets delete How can I make it stop deleting image if file is no_image.png

PHP Code:

public function delete() {
        $json = array();

        if (!$json) {

            foreach ($this->input->post('path') as $path) {
                $no_image_check = $this->config->item('image_path') . 'catalog/no_image.jpg';
                $no_image_cache_check = $this->config->item('image_cache_path') . 'catalog/no_image.jpg';

                if (isset($no_image_check)) {
                    $json['error'] = 'You cannot remove this image';
                }

                if (isset($no_image_cache_check)) {
                    $json['error'] = 'You cannot remove this image';
                }

                if (is_dir($this->config->item('image_path') . $path)) {
                    rmdir($this->config->item('image_path') . $path);
                    rmdir($this->config->item('image_cache_path') . $path);
                } elseif (is_file($this->config->item('image_path') . $path)) {
                    unlink($this->config->item('image_path') . $path);
                    unlink($this->config->item('image_cache_path') . $path);
                }
            }

            $json['success'] = 'Your Selected File Has Been Removed!';
        }

$this->output->set_content_type('Content-Type: application/json');
$this->output->set_output(json_encode($json));

} 


Any examples on how to solve it would be great.

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!