Validate if a file is selected for upload in codeigniter

Question

Hi I'm having some trouble about the upload file part. Well basically I have a form with upload logo part wherein if a user doesn't select a logo he/she can still update his/her profile at the same time the user can also choose to upload a logo but it has some limitations. Now I don't know how I can validate that part to know if he/she chooses an image or not. Here's my code so far in CI controller:

if (//CHECK IF THERE IS A FILE FOR UPLOAD){
                $new_name = $data['id'];

                $config['upload_path'] = './Logos/';
                $config['allowed_types'] = 'jpg|png|gif';
                $config['max_size'] = '100';
                $config['max_width']  = '100';
                $config['max_height']  = '100';

                $this->load->library('upload', $config);

                    if ( ! $this->upload->do_upload())
                    {
                        array_push($data['error_message'], "You have the following errors in your entry:\n");
                        array_push($data['error_message'], "- Logo must be 100x100 pixels in size not exceeding 100KB with JPG,PNG or GIF format");
                        array_push($data['error_message'], "\nLogo upload failed.");
                        $data['check_error'] = true;
                    }
                    else
                    {
                        $data = array('upload_data' => $this->upload->data());

                        //DO UPDATE PART HERE
                        $file = $data['upload_data']['file_name'];
                        rename($config['upload_path'] . $file, $config['upload_path'] .$new_name.'.jpg');
                        //GO TO SETTINGS
                        $this->load->helper('url');  
                        redirect($data['base'].'settings');
                    }
                }

The part in if is where I wanted to set a validations. I tried some tricks but all of those doesn't work properly.

Here's my view part where if the logo of the certain ID already exists it's just display his/her logo or else displays the default logo:

 <tr>
    <td><p class="titles">Logo</p></td>
    <td>
    <div>
        <input type="text" id="fileName" class="file_input_textbox" readonly="readonly">

        <div class="file_input_div">
          <input type="button" value="Browse" class="file_input_button" />
          <input type="file" class="file_input_hidden" onchange="javascript: document.getElementById('fileName').value = this.value" id="upload" name="userfile" />
        </div>
    </div>
    </td>
</tr>

<tr>
<td>
</td>
<td>
<p class="titles">100px x 100px jpg, png or gif only.</p>
</td>
</tr>

<tr>
<td><p class="titles">Current Logo</p></td>
<td>
    <img src="<?php if(is_array(@getimagesize($base."Logos/".$id.".jpg"))){echo $base."Logos/".$id.".jpg";}else{echo $base."Logos/default.jpg";} ?>"  style="margin:0px 0px 0px 90px;"/>
</td>
</tr>

Answer 1

I usually get native PHP to check if the file is being uploaded before getting CI's upload class to do the job:

if (isset($_FILES['upload_field_name']) && is_uploaded_file($_FILES['upload_field_name']['tmp_name'])) {
    //load upload class with the config, etc...
    $this->load->library('upload', $config);
}