先看效果。
修改前的输出内容：

修改后的输出内容：

修改前的Smarty模板代码：
          {html_options output=$locations values=$locations selected=$selectedLocation}
修改后：
{html_options output=$locations values=$locations selected=$selectedLocation indentation=10}
（必须顶格写）

修改前，输出的<option>标签从第二个开始就没有缩进，而且最后一个<option>标签后还有一个回车，很难看。

附一张修改后的Smarty模板代码的截图：

【修改后的plugins/function.html_options.php全部代码】
<?php
/**
 * Smarty plugin
 *
 * @package    Smarty
 * @subpackage PluginsFunction
 */

/**
 * Smarty {html_options} function plugin
 * Type:     function<br>
 * Name:     html_options<br>
 * Purpose:  Prints the list of <option> tags generated from
 *           the passed parameters<br>
 * Params:
 * <pre>
 * - name       (optional) - string default "select"
 * - values     (required) - if no options supplied) - array
 * - options    (required) - if no values supplied) - associative array
 * - selected   (optional) - string default not set
 * - output     (required) - if not options supplied) - array
 * - id         (optional) - string default not set
 * - class      (optional) - string default not set
 * </pre>
 *
 * @link     http://www.smarty.net/manual/en/language.function.html.options.php {html_image}
 *           (Smarty online manual)
 * @author   Monte Ohrt <monte at ohrt dot com>
 * @author   Ralf Strehle (minor optimization) <ralf dot strehle at yahoo dot de>
 *
 * @param array $params parameters
 *
 * @return string
 * @uses     smarty_function_escape_special_chars()
 */
function smarty_function_html_options($params)
{
    require_once(SMARTY_PLUGINS_DIR . 'shared.escape_special_chars.php');

    $name = null;
    $values = null;
    $options = null;
    $selected = null;
    $output = null;
    $id = null;
    $class = null;
    $indentation = 0;

    $extra = '';

    foreach ($params as $_key => $_val) {
        switch ($_key) {
            case 'indentation':
                $$_key = (int) $_val;
                break;
            case 'name':
            case 'class':
            case 'id':
                $$_key = (string) $_val;
                break;

            case 'options':
                $options = (array) $_val;
                break;

            case 'values':
            case 'output':
                $$_key = array_values((array) $_val);
                break;

            case 'selected':
                if (is_array($_val)) {
                    $selected = array();
                    foreach ($_val as $_sel) {
                        if (is_object($_sel)) {
                            if (method_exists($_sel, "__toString")) {
                                $_sel = smarty_function_escape_special_chars((string) $_sel->__toString());
                            } else {
                                trigger_error("html_options: selected attribute contains an object of class '" . get_class($_sel) . "' without __toString() method", E_USER_NOTICE);
                                continue;
                            }
                        } else {
                            $_sel = smarty_function_escape_special_chars((string) $_sel);
                        }
                        $selected[$_sel] = true;
                    }
                } elseif (is_object($_val)) {
                    if (method_exists($_val, "__toString")) {
                        $selected = smarty_function_escape_special_chars((string) $_val->__toString());
                    } else {
                        trigger_error("html_options: selected attribute is an object of class '" . get_class($_val) . "' without __toString() method", E_USER_NOTICE);
                    }
                } else {
                    $selected = smarty_function_escape_special_chars((string) $_val);
                }
                break;

            case 'strict':
                break;

            case 'disabled':
            case 'readonly':
                if (!empty($params['strict'])) {
                    if (!is_scalar($_val)) {
                        trigger_error("html_options: $_key attribute must be a scalar, only boolean true or string '$_key' will actually add the attribute", E_USER_NOTICE);
                    }

                    if ($_val === true || $_val === $_key) {
                        $extra .= ' ' . $_key . '="' . smarty_function_escape_special_chars($_key) . '"';
                    }

                    break;
                }
            // omit break; to fall through!

            default:
                if (!is_array($_val)) {
                    $extra .= ' ' . $_key . '="' . smarty_function_escape_special_chars($_val) . '"';
                } else {
                    trigger_error("html_options: extra attribute '$_key' cannot be an array", E_USER_NOTICE);
                }
                break;
        }
    }

    if (!isset($options) && !isset($values)) {
        /* raise error here? */

        return '';
    }

    $_html_result = '';
    $_idx = 0;

    if (isset($options)) {
        foreach ($options as $_key => $_val) {
            $_html_result .= smarty_function_html_options_optoutput($_key, $_val, $selected, $id, $class, $_idx, $indentation);
        }
    } else {
        foreach ($values as $_i => $_key) {
            $_val = isset($output[$_i]) ? $output[$_i] : '';
            $_html_result .= smarty_function_html_options_optoutput($_key, $_val, $selected, $id, $class, $_idx, $indentation);
        }
    }

    if (!empty($name)) {
        $_html_class = !empty($class) ? ' class="' . $class . '"' : '';
        $_html_id = !empty($id) ? ' id="' . $id . '"' : '';
        $_html_result = '<select name="' . $name . '"' . $_html_class . $_html_id . $extra . '>' . "\n" . $_html_result . '</select>' . "\n";
    } else {
        $_html_result = preg_replace('/\n$/', '', $_html_result); // remove the last \n
    }

    return $_html_result;
}

function smarty_function_html_options_optoutput($key, $value, $selected, $id, $class, &$idx, $indentation)
{
    if (!is_array($value)) {
        $_key = smarty_function_escape_special_chars($key);
        $_html_result = str_repeat(' ', $indentation) . '<option value="' . $_key . '"';
        if (is_array($selected)) {
            if (isset($selected[$_key])) {
                $_html_result .= ' selected="selected"';
            }
        } elseif ($_key === $selected) {
            $_html_result .= ' selected="selected"';
        }
        $_html_class = !empty($class) ? ' class="' . $class . ' option"' : '';
        $_html_id = !empty($id) ? ' id="' . $id . '-' . $idx . '"' : '';
        if (is_object($value)) {
            if (method_exists($value, "__toString")) {
                $value = smarty_function_escape_special_chars((string) $value->__toString());
            } else {
                trigger_error("html_options: value is an object of class '" . get_class($value) . "' without __toString() method", E_USER_NOTICE);

                return '';
            }
        } else {
            $value = smarty_function_escape_special_chars((string) $value);
        }
        $_html_result .= $_html_class . $_html_id . '>' . $value . '</option>' . "\n";
        $idx ++;
    } else {
        $_idx = 0;
        $_html_result = smarty_function_html_options_optgroup($key, $value, $selected, !empty($id) ? ($id . '-' . $idx) : null, $class, $_idx);
        $idx ++;
    }

    return $_html_result;
}

function smarty_function_html_options_optgroup($key, $values, $selected, $id, $class, &$idx)
{
    $optgroup_html = '<optgroup label="' . smarty_function_escape_special_chars($key) . '">' . "\n";
    foreach ($values as $key => $value) {
        $optgroup_html .= smarty_function_html_options_optoutput($key, $value, $selected, $id, $class, $idx);
    }
    $optgroup_html .= "</optgroup>\n";

    return $optgroup_html;
}

详细的代码修改内容：

} else {
        //$_html_result = preg_replace('/\n$/', '', $_html_result); // remove the last \n
    }
    $_html_result = trim($_html_result);

这个用trim也可以达到同样的效果。而且用trim的话会把开头的空格和末尾的\n都去掉，因此这样一来{html_options output=$locations values=$locations selected=$selectedLocation indentation=10}这个就不用顶格写了，该在哪写就在哪儿写。