Programmatically save image together with its ALT

Question

I am not sure what is the benefit of using system_retrieve_file mentioned on Save image from URL to a field from a custom module, so I just use the following simple code to save image programmatically:

    $file = file_save_data(file_get_contents($url), file_default_scheme().'://field/image/'.basename($url));
    $file->status = 1;
    $node->field_image['und'][0] = (array)$file;
    node_save($node);

Works fine, so now I am trying to figure out how to save the enabled alt value which is stored in $alt variable.

When I output what the $file array contains with dsm(print_r($file,true)); it shows only:

stdClass Object
(
[fid] => 9
[uri] => public://field/image/150304192032_monalisa_624x351_afp_0.jpg
[filename] => 150304192032_monalisa_624x351_afp.jpg
[filemime] => image/jpeg
[uid] => 1
[status] => 1
[timestamp] => 1425596902
[filesize] => 28642
)

Unfortunately, it doesn't contain neither title or alt. Could anyone help me to get this sorted out? Thanks!

Answer 1

As far as Drupal 8 is concerned, there is another solution :

//    $file : my File Entity
//    $node : my (Node) Entity having an Image File field associated
$node->field_my_image_field[] = [
 'target_id' => $file->id(),
 'alt' => 'Alt. text',
];
$node->save();

Well, I think that 'width', 'height' and 'title' are also available in the setting array (but target_id seems required). cf: https://api.drupal.org/api/drupal/core%21modules%21image%21src%21Plugin%21Field%21FieldType%21ImageItem.php/class/ImageItem/8.2.x (look at the source code, generateSampleValue() method).

Answer 2

Ok, I've got this done by using the following code after node_save():

$update = db_update('field_data_field_image')
  ->fields(array(
    'field_image_alt' => $alt,
  ))
  ->condition('field_image_fid', $file->fid)
  ->execute();

It seems this is the only way. More detailed findings are given on https://www.drupal.org/node/2447091