Uploading file into directory

Does somebody knows how to upload a file into a specific folder?

I'm working on a blog page in which I need to display the picture that comes with the published post. Right now I made it to show a "noimage.jpg" if there's not image uploaded but so far all the posts that I have published have their own images.


It keeps showing the "noimage.jpg" file. The sending function its not even working(as all the files that I upload are nt being sent into the folder which I specified), can somebody guide me in how to fix this?

PHP Code:

           $slug = str_replace(' ', '-', $this->input->post('title'));
            $slug = strtolower($slug);

            // Upload Image
            $upload['upload_path'] = './assets/img/posts';
            $upload['allowed_types'] = 'gif|jpg|png';
            $upload['max_size'] = '2048';
            $upload['max_width'] = '2000';
            $upload['max_height'] = '2000';
    
            $this->load->library('upload', $upload);
    
            if (!$this->upload->do_upload('post_image')) {
                $filename = './assets/img/noimage.jpg';
            } else {
                $upload_data = $this->upload->data();
                $filename = $upload_data['file_name'];
                
            }
            
            // Page Data
            $data = array(
                'title'            => $this->input->post('title'),
                'slug'            => $slug,
                'subject_id'    => $this->input->post('subject_id'),
                'body'            => $this->input->post('body'),
                'is_published'    => $this->input->post('is_published'),
                'is_featured'    => $this->input->post('is_featured'),
                'in_menu'        => $this->input->post('in_menu'),
                'user_id'        => $this->session->userdata('user_id'),
                'order'            => $this->input->post('order'),
                'post_image'    => $filename,
            );
            
            // Insert Page
            $this->Post_model->add($data); 


here is my view in which I create/add new posts:

PHP Code:

<h2 class="page-header">Add Post</h2>
<?php echo validation_errors('<p class="alert alert-danger">'); ?>
<?php echo form_open_multipart('admin/posts/add'); ?>
    <!-- Page Title -->
    <div class="form-group">
        <?php echo form_label('Post Title', 'title'); ?>
        <?php
            $data = array(
                'name' => 'title',
                'id'    => 'title',
                'maxlength'    => '100',
                'class'        => 'form-control',
                'value'        => set_value('title')
            );
        ?>
        <?php echo form_input($data); ?>
    </div>
    
    <!-- Page Img -->
    <div class="form-group">  
        <?php echo form_label('Upload Image', 'post_image') ?>
        <?php
            $data = array(
                'name'    => 'post_image',
                'class'    => 'form-control',
                'value'    => set_value('post_image')
            );
        ?>
        <?php echo form_upload($data); ?>
    </div>

    <!-- Page Subject -->
    <div class="form-group">
        <?php echo form_label('Post Category', 'subject_id'); ?>
        <?php echo form_dropdown('subject_id', $subject_options, 0, array('class' => 'form-control')); ?>
    </div>

    <!-- Page Body -->
    <div class="form-group">
        <?php echo form_label('Body', 'body'); ?>
        <?php
            $data = array(
                'name'          => 'body',
                'id'            => 'body',
                'class'         => 'form-control',
                'value'            => set_value('subject')
            );
        ?>
        <?php echo form_textarea($data); ?>
    </div>

    <!-- Publish -->
    <div class="form-group">
        <?php echo form_label('Published', 'is_published'); ?>
        <?php echo form_radio('is_published', 1, TRUE); ?> Yes 
        <?php echo form_radio('is_published', 0, FALSE); ?> No
    </div>

    <!-- Feature -->
    <div class="form-group">
        <?php echo form_label('Feature', 'is_featured'); ?>
        <?php echo form_radio('is_featured', 1, FALSE); ?> Yes 
        <?php echo form_radio('is_featured', 0, TRUE); ?> No
    </div>

    <!-- Menu -->
    <div class="form-group">
        <?php echo form_label('Add To Menu', 'in_menu'); ?>
        <?php echo form_radio('in_menu', 1, TRUE); ?> Yes 
        <?php echo form_radio('in_menu', 0, FALSE); ?> No
    </div>

    <!-- Order -->
    <div class="form-group">
        <?php echo form_label('Order', 'order'); ?>
        <input class="form-control" name="order" id="order" type="number">
    </div>

    <?php echo form_submit('mysubmit', 'Add Post', array('class' => 'btn btn-primary')); ?>
<?php echo form_close(); ?>
<script>
/*TinyMce editor*/
    tinymce.init({
    selector: "textarea",
    theme: "modern",
    image_advtab: true,    
    plugins: [
         "advlist autolink link image lists charmap  preview hr anchor pagebreak spellchecker",
         "searchreplace wordcount visualblocks visualchars code fullscreen insertdatetime  nonbreaking",
         "table contextmenu directionality template paste textcolor"
            ],
    toolbar: "insertfile undo redo | styleselect | bold underline italic | alignleft aligncenter alignright alignjustify | bullist numlist outdent indent | image link | code fullscreen"
     });
</script> 


I do Front-End development most of the time 

Check if the folder you want to write to, has the right permissions (777).