想知道是否有人可以解释为什么作者在这段代码中使用ob\\u start（）和ob\\u clean（）在WordPress中构建导入/导出页面？

因为我想将此代码集成到另一个插件中，并且我想将代码分离到不同的文件中，所以我需要将ob\\u start（）放在哪里才能工作？

<?php
/*
Plugin Name: I/E Option
Plugin URI: http://wp.tutsplus.com/
Description: This is a sample plugin with backup and restore options feature.
Author: Lee Pham
Version: 1.0
Author URI: https://twitter.com/leephamj
*/

function register_ie_option() {
    ob_start();
    add_menu_page(\'IE Option Page\', \'IE Option\', \'activate_plugins\', \'ie-option\', \'ie_option_page\', \'\');    
    add_submenu_page(\'ie-option\', \'Import\', \'Import\', \'activate_plugins\', \'ie-import-option\', \'ie_import_option_page\');
    add_submenu_page(\'ie-option\', \'Export\', \'Export\', \'activate_plugins\', \'ie-export-option\', \'ie_export_option_page\'); 
}

/*  
 *  Main page
 */
function ie_option_page() {
?>
    <div class="wrap">
        <div id="icon-tools" class="icon32"><br /></div>
        <h2>Backup & Restore </h2>
        <p>This is only a sample plugin that demonstrate how to create a simple import/export feature for your own templates or plugins.</p>
        <p>Hope it useful for you!</p>
        <p>Get in touch with me:</p>
        <ul>
            <li>E-mail: [email protected]</li>
            <li>Twitter: <a href="http://twitter.com/leephamj">@leephamj</a></li>
            <li>Facebook: <a href="http://facebook.com/tungchen93">Lee Pham</a></li>
        </ul>
    </div>
<?php   
}

/*  
 *  Import feature
 */
function ie_import_option_page() {
?>
    <div class="wrap">
        <div id="icon-tools" class="icon32"><br /></div>
        <h2>Import</h2>
        <?php
            if (isset($_FILES[\'import\']) && check_admin_referer(\'ie-import\')) {
                if ($_FILES[\'import\'][\'error\'] > 0) 
                    wp_die("Error happens");        
                else {
                    $file_name = $_FILES[\'import\'][\'name\'];
                    $file_ext = strtolower(end(explode(".", $file_name)));
                    $file_size = $_FILES[\'import\'][\'size\'];
                    if (($file_ext == "json") && ($file_size < 500000)) {
                        $encode_options = file_get_contents($_FILES[\'import\'][\'tmp_name\']);
                        $options = json_decode($encode_options, true);
                        foreach ($options as $key => $value) {
                            update_option($key, $value);    
                        }
                        echo "<div class=\'updated\'><p>All options are restored successfully.</p></div>";
                    }   
                    else 
                        echo "<div class=\'error\'><p>Invalid file or file size too big.</p></div>";
                }
            }
        ?>
        <p>Click Browse button and choose a json file that you backup before.</p>
        <p>Press Restore button, Wordpress do the rest for you.</p>
        <form method=\'post\' enctype=\'multipart/form-data\'>
            <p class="submit">
                <?php wp_nonce_field(\'ie-import\'); ?>
                <input type=\'file\' name=\'import\' />
                <input type=\'submit\' name=\'submit\' value=\'Restore\'/>
            </p>
        </form>
    </div>
<?php
}

/*  
 *  Export feature
 */
function ie_export_option_page() {
    if (!isset($_POST[\'export\'])) { 
?>
        <div class="wrap">
            <div id="icon-tools" class="icon32"><br /></div>
            <h2>Export</h2>
            <p>When you click <tt>Backup all options</tt> button, system will generate a JSON file for you to save on your computer.</p>
            <p>This backup file contains all configution and setting options on our website. Note that it do <b>NOT</b> contain posts, pages, or any relevant data, just your all options.</p>
            <p>After exporting, you can either use the backup file to restore your settings on this site again or another Wordpress site.</p>
            <form method=\'post\'>
            <p class="submit">
                <?php wp_nonce_field(\'ie-export\'); ?>
                <input type=\'submit\' name=\'export\' value=\'Backup all options\'/>
            </p>
            </form>
        </div>
<?php 
    } elseif (check_admin_referer(\'ie-export\')) {

        $blogname = str_replace(" ", "", get_option(\'blogname\'));
        $date = date("m-d-Y");
        $json_name = $blogname."-".$date; // Namming the filename will be generated.

        $options = get_alloptions(); // Get all options data, return array

        foreach ($options as $key => $value) {
            $value = maybe_unserialize($value);
            $need_options[$key] = $value;
        }

        $json_file = json_encode($need_options); // Encode data into json data

        ob_clean();
        echo $json_file;
        header("Content-Type: text/json; charset=" . get_option( \'blog_charset\'));
        header("Content-Disposition: attachment; filename=$json_name.json");
        exit();
    }
}
add_action(\'admin_menu\', \'register_ie_option\');