codeigniter alert if image size exceeds - php

Question

Hi I have this code for uploading an image. I can perfectly add the image but I want to add restrictions and there will an alert that will pop up if image size exceeds but I don't know how can add I alert if image size exceeds. please help me
Here's my code:
CONTROLLERS:
public function upload_file()
{
$filename = 'r_image';
$status = "";
$msg = "";
$config['upload_path'] = 'img/recipes/';
$config['allowed_types'] = 'gif|jpg|png';
$config['max_size'] = 1024 * 8 ;
$config['encrypt_name'] = true;
$this->load->library('upload',$config);
if (!$this->upload->do_upload($filename))
{
$stats = 'error';
$msg = $this->upload->display_errors('', '');
}else{
$uploadData = $this->upload->data('file_name');
if($uploadData['file_name'])
{
$thumnail = 'img/recipes/'.$uploadData['file_name'];
}else{
$thumnail = 'No thumnbail uploaded!';
}
$updateThumbData = array('recipe_id' => $recipe_id,
'r_image' => $thumnail
);
$this->products_model->updataRecipeThumnail($updateThumbData);
redirect('dashboard/view_product');
} /* upload_file() */
}

Answer 1

for uploading files you must use POST method. read this w3schools file upload.
if($_FILES['Your_POST_name']['size']>1024 * 8 )// to check what is your post name print_r($_FILES);
{
$this->session->set_flashdata('msg', '<div class="alert alert-danger alert-dismissible fade in" role="alert"><button type="button" class="close" data-dismiss="alert" aria-label="Close"><span aria-hidden="true">×</span></button>Image is too big!</div>');
redirect('dashboard/view_product');
}
and in your view_product's view file, add following code to display error
<?php echo $this->session->flashdata('msg'); ?>
Important things to remember while dealing with file uploads in php.
Make sure that the form uses method="post"
The form also needs the following attribute:
enctype="multipart/form-data". It specifies which content-type to use
when submitting the form
Without the requirements above, the file upload will not work.