File was not uploading in codeigniter - php

Question

I am uploading images in codeigniter. my file is not getting uploaded. i dont know where i am doing wrong. please find in below code
Html:
<form method="post" enctype="multipart/form-data" action="<?php echo base_url(); ?>assign_user/addStartPopup">
<div class="col-lg-6">
<div class="form-group">
<label for="image">
<input type="radio" id="image" name="start_img" onclick="rightfilefunction(1);" checked> <label for="image"> <span style="top: -2px;position: relative;">Image upload</span></label>
<label for="video" class="green">
<input type="radio" id="video" name="start_img" onclick="rightfilefunction(2);">
<span style="top: -2px;position: relative;">Video</span>
</label>
</div>
<div class="form-group" id="imageId">
<input type="file" name="imageupload" class="form-control">
</div>
<div class="form-group" id="videoId" style="display:none">
<input type="text" name="video_upload" class="form-control">
</div>
<div class="form-group">
<button type="submit" class="btn btn-primary"> Save </button>
</div>
</div>
</form>
Model:
public function startPopup(){
$createdOn = date('Y-m-d H:i:s');
if($_FILES['imageupload']['size'] != 0)
{
$files = $_FILES;
$config = array();
$config['upload_path'] = "startpage/";
$config['allowed_types'] = "png|jpg|gif";
$config['max_size'] = "5000";
$this->load->library('upload',$config);
$this->upload->initialize($config);
if($this->upload->do_upload('imageupload')){
$imgdata = $this->upload->data();
$image_config=array();
$image_config["image_library"] = "gd2";
$image_config['overwrite'] = TRUE;
$image_config["source_image"] = $imgdata["full_path"];
$image_config['create_thumb'] = FALSE;
$image_config['maintain_ratio'] = TRUE;
$image_config['new_image'] = $imgdata["file_path"].$imgdata["file_name"];
$image_config['quality'] = "95%";
$image_config['width'] = 170;
$image_config['height'] = 170;
$this->load->library('image_lib',$image_config);
$this->image_lib->initialize($image_config);
$this->image_lib->resize();
$logo = 'startpage/'.$imgdata["file_name"];
$query = $this->db->query("INSERT INTO `startpop` (content_view, created_on) VALUES ('$logo', '$createdOn')");
if($query){
return 1;
}
}else
{
echo "not uploaded";
}
}else{
$prv = $this->input->post('video_upload');
$query = $this->db->query("INSERT INTO `startpop` (content_view, created_on) VALUES ('$prv', '$createdOn')");
if($query){
return 1;
}
}
}
Controller:
public function addStartPopup(){
$result = $this->model->startPopup();
if($result > 0){
$data['mgs'] = "Added Successfully ..!";
$this->load->view('admin/startPage',$data);
}
}
From this above code, i am getting the error "not uploaded". can any one tell me where i am doing wrong