Programmatically add image already in public to node

Question

I have very little experience working with Drupal and it may be possible that I'm missing something very basic here.

I have created a module to add/update nodes pro-grammatically from an XML file, this nodes have a file for images. For every node there's a French version and an English version, this means that they share the same images. When I import these nodes I would like to avoid refetching the images (since those are already into the public:// folder) and populate only the image field.

The first run goes smoothly, the images are fetched and saved from URL for all the English nodes using this code:

if(!file_exists("public://" . $name)) {
    $file_temp = file_get_contents($URL);
    $file_temp = file_save_data($file_temp, "public://" . $name, FILE_EXISTS_REPLACE);
}

$node->field_image[LANGUAGE_NONE][$k]['fid'] = $file_temp->fid;
$node->field_image[LANGUAGE_NONE][$k]['title'] = $name;

The second round, for the french nodes, what I've done is:

else {
    $file_temp = new stdClass();
    // Get the image id corresponding to the $name parameter, returns string.
    $file_temp->fid = _xml_importer_get_image_id($name, $table, $fid, $title);
}

$node->field_image[LANGUAGE_NONE][$k]['fid'] = $file_temp->fid;
$node->field_image[LANGUAGE_NONE][$k]['title'] = $name;

This works, in a sense, meaning that the fields are populated correctly and the image are shared between the nodes, the problem is that I get warning and notices for this part.

This is the full dump:

Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of /drupal/includes/entity.inc). Notice: Trying to get property of non-object in file_field_presave() (line 220 of drupal/modules/file/file.field.inc). Strict warning: Creating default object from empty value in file_field_presave() (line 221 of drupal/modules/file/file.field.inc). Notice: Undefined property: stdClass::$uri in file_save() (line 566 of drupal/includes/file.inc). Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of drupal/includes/entity.inc). Notice: Trying to get property of non-object in file_field_presave() (line 220 of drupal/modules/file/file.field.inc). Strict warning: Creating default object from empty value in file_field_presave() (line 221 of drupal/modules/file/file.field.inc). Notice: Undefined property: stdClass::$uri in file_save() (line 566 of drupal/includes/file.inc). SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '' for key 'uri' Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of drupal/includes/entity.inc). Notice: Trying to get property of non-object in file_field_presave() (line 220 of drupal/modules/file/file.field.inc). Strict warning: Creating default object from empty value in file_field_presave() (line 221 of drupal/modules/file/file.field.inc). Notice: Undefined property: stdClass::$uri in file_save() (line 566 of drupal/includes/file.inc). Warning: array_flip() [function.array-flip]: Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of drupal/includes/entity.inc). Notice: Trying to get property of non-object in file_field_presave() (line 220 of drupal/modules/file/file.field.inc). Strict warning: Creating default object from empty value in file_field_presave() (line 221 of drupal/modules/file/file.field.inc). Notice: Undefined property: stdClass::$uri in file_save() (line 566 of drupal/includes/file.inc).

I looked for this kind of warnings/notices and I found out that somewhere I'm passing some parameters not in a correct way (e.g. arrays instead of strings) and for me doesn't make sense. My guess is that not invoking file_save_data has some effect on the file_managed table and gives missing or malformed parameter, anyway with my poor experience I may be very well mistaking.

This is the full code snippet I'm using:

for($k=0; $k<sizeof($file_list); $k++) {
    if(!file_exists("public://" . $file_list[$k]->name)) {
        $file_temp = file_get_contents($URL);
        $file_temp = file_save_data($file_temp, "public://" . $file_list[$k]->name, FILE_EXISTS_REPLACE);
    }
    else {
        $file_temp = new stdClass();
        // Get the image id corresponding to the $name parameter, returns string.
        $file_temp->fid = _xml_importer_get_image_id($file_list[$k]->name, $table, $fid, $title);
    }
    $node->field_image[LANGUAGE_NONE][$k]['fid'] = $file_temp->fid;
    $node->field_image[LANGUAGE_NONE][$k]['title'] = $file_list[$k]->name;
}

And this is the function _xml_importer_get_image_id:

_xml_importer_get_image_id($image_name, $table, $field, $title_field) {

    $query = db_select($table, 'ill')
        ->condition('ill.' . $title_field, $image_name, '=')
        ->fields('ill', array($field))
        ->execute()
        ->fetchCol();

    if(empty($query)) {
            return false;
    }
    else{
        return (string)$query[0];
    }
}

Answer 1

I found that with my snippet I was totally bypassing the Drupal file management system, I corrected the issue in this way:

else {
    $file_temp = file_load(_xml_importer_get_image_id($image_xpath[$k]->value, $table, $field, $title));
}
$node->field_image[LANGUAGE_NONE][$k]['fid'] = $file_temp->fid;
$node->field_image[LANGUAGE_NONE][$k]['title'] = $file_list[$k]->name;

Another problem was that there was the same image name twice inside the XML file, had to check for duplicate to avoid breaking some unicity constraint from the database.