1 system.api.php hook_file_validate(File $file)

Check that files meet a given criteria.

This hook lets modules perform additional validation on files. They're able to report a failure by returning one or more error messages.


File $file: The file entity being validated.

Return value

An array of error messages. If there are no problems with the file return: an empty array.

See also


Related topics


core/modules/system/system.api.php, line 2285
Hooks provided by Backdrop core and the System module.


function hook_file_validate(File $file) {
  $errors = array();

  if (empty($file->filename)) {
    $errors[] = t("The file's name is empty. Please give a name to the file.");
  if (strlen($file->filename) > 255) {
    $errors[] = t("The file's name exceeds the 255 characters limit. Please rename the file and try again.");

  return $errors;