使用http://codex.wordpress.org/Settings_API 要向现有组“general”添加新设置，请执行以下操作：

add_action( \'admin_init\', \'register_my_setting\' );
function register_my_setting()
{
    add_settings_field(\'foo\', \'Foo settings\', \'foo_function\', \'general\', \'default\', array(\'label_for\' => \'foo\'));
    register_setting(\'general\', \'foo\', \'foo value\');
}
function foo_function()
{
    echo \'<input name="foo" id="foo" value="" class="regular-text ltr">\';
}