How can I replace an image using a Form API?

Question

I have a form that works great for adding fields, including and image, to a node and saving it.

I want to allow users to edit their fields and change the data, including their image. I figure there is some way to retrieve and display the current image and then allow the user to upload and save/replace the image with a new one. I can't figure out how to show a preview of the existing image on the Edit form. I assume somewhere I should use File_Exists_Replace, but the rest is an overwhelming mystery.

Here is the code I use for the original form:

  $form['logo'] = array(
  '#title' => t('Image'),
  '#type' => 'managed_file',
  '#description' => t('Only image files will be allowed.'),
  '#default_value' => variable_get('logo', ''),
  '#upload_location' => 'public://misc/media',
  '#upload_validators'  => array(
    'file_validate_extensions' => array('png gif jpg jpeg'),
    'file_validate_size' => array(2*1024*1024),
    )
  );

And the submit function:

    // Load the file via file.fid.
    $file = file_load($form_state['values']['logo']);
    // Change status to permanent.
    $file->status = FILE_STATUS_PERMANENT;
    // Save.
    file_save($file);
    // Record that the module (in this example, cformtwo module) is using the file. 
    file_usage_add($file, 'cformtwo', 'node', 1);  
...
    node_submit($node);
    node_save($node);

I have spent days trying to figure out how to do this.

Answer 1

Your 'logo' variable will be a file id, referring to a row in the file_managed table, so you can use the file_load() function to load the file object, create an image with the details, and attach it to your form field.

This is a (very) basic example:

$logo = variable_get('logo');

$image = '';
if ($logo) {
  // Load the file object
  $file = file_load($logo);

  // Get a thumbnail of the image (just an example)
  $args = array('style_name' => 'thumbnail', 'path' => $file->uri, 'alt' => 'Alt text');
  $image = theme('image_style', $args);
}

// Prepend it to your field
$form['logo'] = array(
  '#title' => t('Image'),
  '#type' => 'managed_file',
  '#description' => t('Only image files will be allowed.'),
  '#default_value' => $logo,
  '#upload_location' => 'public://misc/media',
  '#upload_validators'  => array(
    'file_validate_extensions' => array('png gif jpg jpeg'),
    'file_validate_size' => array(2*1024*1024),
  ),
  '#prefix' => $image
);