Creating an Uploads folder with post ID

Question

I'm creating an online area for our staff to create new posts in WordPress to share lesson resources with students. I'm currently developing a section whereby students are able to upload documents to the custom post (front end form) and these uploads are then stored in the Uploads directory.

Currently, I've got it to upload to the directory but I can't work out how to create a new folder based on what the Post ID is.

Any ideas greatly appreciated.

include_once plugin_dir_path( __FILE__ ).'upload.php';

function assignment_uploads(){

  global $post;

  echo '
    <form method="post" enctype="multipart/form-data" action="">
        <input type="file" name="file_upload">
        <input type="hidden" name="lesson_id" value="'. $post->ID.'">
        <input type="submit" name="upload_submitted">
    </form>
  ';
}
add_shortcode( 'student_submission_upload_form', 'assignment_uploads' );

// store post id in var
$lesson_id = $_POST['lesson_id']; 

function create_uploads_folder() {
    $upload_dir = $uploadFolder['basedir'];
    $upload_dir = $upload_dir . '/submissions/'.$lesson_id;
    if (! is_dir($upload_dir)) {
       mkdir( $upload_dir, 0705 );
    }
}
register_activation_hook( __FILE__, 'create_uploads_folder' );

// Upload file
if(!move_uploaded_file($_FILES['file_upload']['tmp_name'], $uploadFolder['basedir'] . '/submissions/' . $lesson_id . '/' . $_FILES['file_upload']['name'])){
    die('Error uploading file - check destination is writeable');
}

Answer 1

I wrote this code for you:

global $lesson_id;
$lesson_id = $_POST['lesson_id']; 

function create_uploads_folder() {
    global $lesson_id;

    $upload_dir = wp_upload_dir();
    $upload_dir = $upload_dir['basedir'];
    $upload_dir = $upload_dir . '/submissions/'. $lesson_id;
    if ( ! is_dir( $upload_dir ) ) {
        wp_mkdir_p( $upload_dir );
    }
}

register_activation_hook( __FILE__, 'create_uploads_folder' );

// Upload file
$uploadFolder = wp_upload_dir();
if ( ! move_uploaded_file($_FILES['file_upload']['tmp_name'], $uploadFolder['basedir'] . '/submissions/' . $lesson_id . '/' . $_FILES['file_upload']['name'])){
    die('Error uploading file - check destination is writeable');
}