drupal文件上传表单的例子

function upload_form() {
    $form = array();
    // If this #attribute is not present, upload will fail on submit
    $form['#attributes']['enctype'] = 'multipart/form-data';
    $form['file_upload'] = array(
            '#title' => t('Upload file'),
            '#type'  => 'file',
    );
    $form['submit_upload'] = array(
            '#type'  =>  'submit',
            '#value'  =>  'Submit'
    );
    return $form;
}

function upload_submit($form, &$form_state) {
    $validators = array();
    $dest = file_directory_path();
    $file = file_save_upload('file_upload', $validators, $dest);
    //$file will be 0 if the upload doesn't exist, or the $dest directory
    //isn't writable
    if ($file != 0) {
        $file->filepath; // 文件相对路径
    }
    else {
        form_set_error('myform', t("Failed to save the file."));
    }
}