Codeigniter File upload validation undefined index - php

Question

I don't know where I got wrong but I couldn't find it out.
I have a form validation with a callback file check validation function
My Add_Post Function:
public function add_post()
{
$validation = array (
array(
'field' => 'post_title',
'label' => 'Post title',
'rules' => 'trim|required|alpha_numeric'
),
array(
'field' => 'headerimage',
'rules' => 'required|callback_file_check'
),
array(
'field' => 'post_desc',
'label' => 'Post Description',
'rules' => 'trim|required|alpha_numeric'
),
array(
'field' => 'post_content',
'label' => 'Post content',
'rules' => 'trim|required'
)
);
$this->form_validation->set_rules($validation);
if($this->form_validation->run()===FALSE)
{
$info['errors'] = validation_errors();
$info['success'] = false;
}
else
{
$config = array(
"upload_path" => "./uploads/blog_images",
"max_size" => "2048000",
"allowed_types"=> "gif|png|jpg|jpeg",
"file_name" => 'header_'.substr(md5(rand()),0,7),
"overwrite" => false
);
$this->load->library('upload', $config);
if($this->upload->do_upload('file'))
{
$uploadFile = $this->upload->upload_data();
$uploadFileName = $uploadFile['file_name'];
$data = array(
"post_title" => $this->input->post('post_title'),
"post_content" => $this->input->post('post_content'),
"post_image" => $uploadFileName,
"post_created" => $this->input->post('time')
);
$this->Blog_model->add_post($data);
}
$info['success'] = true;
$info['message'] = "Successfully added blog post";
}
$this->output->set_content_type('application/json')->set_output(json_encode($info));
}
Callback function:
public function file_check($str){
$allowed_mime_type_arr = array('application/pdf', 'image/gif', 'image/jpeg', 'image/pjpeg', 'image/png', 'image/x-png');
$mime = get_mime_by_extension($_FILES['headerimage']['name']);
if(isset($_FILES['headerimage']['name']) && $_FILES['headerimage']['name'] != "") {
if(in_array($mime, $allowed_mime_type_arr)) {
return true;
} else {
$this->form_validation->set_message('file_check', 'Please select only pdf/gif/jpg/png file.');
return false;
}
} else {
$this->form_validation->set_message('file_check', 'Please choose a file to upload.');
return false;
}
}
Here's for the view part:
<?php echo form_open_multipart('Blog/file_check',array("class"=>"form-horizontal","id"=>"blogform")); ?>
<div class="row">
<div class="col-md-6">
<input type="text" placeholder="Enter your post title" name="post_title" class="form-control">
</div>
<div class="col-md-6 form-group">
<label for="file" class="control-label col-md-4">Select header image:</label>
<div class="col-md-8">
<input type="file" name="headerimage" id="file" accept="image/*" />
</div>
</div>
</div>
<input type="text" placeholder="Enter your post description" name="post_desc" class="form-control">
<label class="control-label text-muted">Post Body:</label>
<div>
<textarea id="post_content" name="content"></textarea>
</div>
<button class="btn btn-default pull-right" type="button" id="save-post"><i class="fa fa-save"></i> Save Post</button>
<div class="clearfix"></div>
<?php echo form_close(); ?>
My Ajax code:
$(document).on('click','#save-post',function(){
$post_content = $('#post_content').summernote('code');
$time = $('#time').text();
$.ajax({
url:site_url('Blog/add_post'),
data: $('#blogform').serialize() + "&post_content=" + $post_content + "&time=" + $time,
type: "POST",
dataType: 'json',
encode: true,
success: function(data){
if(!data.success) {
if(data.errors) {
$('#blog-message').html(data.errors).addClass('alert alert-danger');
}
} else {
alert(data.message);
}
}
});
});
Input FileName Checked: I already checked the input name and it's the same.
Image Size: I checked for some related question of mine which is undefined index on file validation and they said image size must be big but I use a small size image sample.
I used Krajee's File Input Plugin.