Checks that the filename ends with an allowed extension.
$file: A Drupal file object.
$extensions: A string with a space separated list of allowed extensions.
An array. If the file extension is not allowed, it will contain an error message.
function file_validate_extensions(stdClass $file, $extensions) {
$errors = array();
$regex = '/\\.(' . preg_replace('/ +/', '|', preg_quote($extensions)) . ')$/i';
if (!preg_match($regex, $file->filename)) {
$errors[] = t('Only files with the following extensions are allowed: %files-allowed.', array(
'%files-allowed' => $extensions,
));
}
return $errors;
}