I need upload file from frontend and add this file to email address with attach, but have always error...

PHP Warning: file_get_contents(/tmp/php3ItUlo): failed to open stream: No such file or directory

Action where form is created:

FileForm.php -> extends Page

function fileSendForm() {
        $upload = new FileField('picture', 'Add your file *');
       
        $fields = new FieldList(array($upload));

        $actions = new FieldList( new FormAction('SendFileForm', 'Send'));
        $form = new Form($this, 'SendFileForm', $fields, $actions);
        return $form;
}

Form Post to that function:
FileForm_Controller.php -> extends Page_Controller

function SendFileForm($data) {

$email = new Email(ltrim($from), ltrim($to), ltrim($assunto_field), $body);

if ( !$_FILES["picture"]["error"] > 0 ) {
error_log( "Name: " . $_FILES["picture"]["name"]);
error_log( "Type: " . $_FILES["picture"]["type"]);
error_log( "Size: " . ($_FILES["picture"]["size"] / 1024) . " kB");
error_log( "Save in: " . $_FILES["picture"]["tmp_name"]);
move_uploaded_file($_FILES["picture"]["tmp_name"], $_FILES["picture"]["name"]);
            }
$imagedata = file_get_contents($_FILES["picture"]["tmp_name"]);

if (is_uploaded_file($_FILES["picture"]["tmp_name"])) {
  $email->attachFile($_FILES["picture"]["tmp_name"], $_FILES["picture"]["name"]);
}

$email->send();
}

The error_log when submit the file 013.jpg have this

Nome: 013.jpg
Type: image/jpeg
Size: 91.654296875 kB
Save in: /tmp/php3ItUlo
PHP Warning:  file_get_contents(/tmp/php3ItUlo): failed to open stream: No such file or directory

Email was sent but without have attach file

What do wrong?

It looks like SilverStripe is trying to store the uploaded image in your server's temp directory and for some reason isn't allowed to. Have you tried to create a "silverstripe-cache" directory in your web root?