为 WordPress 小工具功能添加CSS类选项

WordPress 小工具可以重复使用，相同的小工具样式也是相同的，如果想自定义某个前台添加的小工具样式，与其它不同，可以通过查看源代码，找到它的id，比如搜索小工具会看到类似的：

<section id="search-2" class="widget widget_search">

其中search-2就是这个小工具的ID，可以用#search-2定义样式，不过这个后缀的编号并不是固定的，下次添加可能会变，需要再次编辑之前的样式，有些麻烦。

可以通过下面的代码，给现有的小工具统一增加CSS类选项，将代码添加到当前主题函数模板functions.php中即可，效果如图：

代码一　只加一个CSS类选项

function zm_widget_form_extend( $instance, $widget ) {
  if ( !isset($instance['classes']) )
		$instance['classes'] = null;
		$row = "<p>\n";
		$row .= "\t<label for='widget-{$widget->id_base}-{$widget->number}-classes'>CSS类</label>\n";
		$row .= "\t<input type='text' name='widget-{$widget->id_base}[{$widget->number}][classes]' id='widget-{$widget->id_base}-{$widget->number}-classes' class='widefat' value='{$instance['classes']}'/>\n";
		$row .= "</p>\n";
		echo $row;
	return $instance;
}
add_filter('widget_form_callback', 'zm_widget_form_extend', 10, 2);
 
function zm_widget_update( $instance, $new_instance ) {
	$instance['classes'] = $new_instance['classes'];
	return $instance;
}
add_filter( 'widget_update_callback', 'zm_widget_update', 10, 2 );
 
function zm_dynamic_sidebar_params( $params ) {
	global $wp_registered_widgets;
	$widget_id    = $params[0]['widget_id'];
	$widget_obj    = $wp_registered_widgets[$widget_id];
	$widget_opt    = get_option($widget_obj['callback'][0]->option_name);
	$widget_num    = $widget_obj['params'][0]['number'];
 
	if ( isset($widget_opt[$widget_num]['classes']) && !empty($widget_opt[$widget_num]['classes']) )
		$params[0]['before_widget'] = preg_replace( '/class="/', "class=\"{$widget_opt[$widget_num]['classes']} ", $params[0]['before_widget'], 1 );
	return $params;
}
add_filter( 'dynamic_sidebar_params', 'zm_dynamic_sidebar_params' );

代码二　添加ID及CSS类下拉选项

function zm_widget_form_extend( $instance, $widget ) {
	if ( !isset( $instance['classes'] ) )
		$instance['classes'] = null;
 
	if ( !isset( $instance['custom_id'] ) )
		$instance['custom_id'] = null;
 
	$class_prefix = 'widget-'; 
	$myclass = array(
		'default'  => '默认',
		'blue'     => '蓝色',
		'yellow'   => '黄色',
		'black'    => '黑色',
	);
 
	$row = "<p>\n";
	$row .= "\t<label for='widget-{$widget->id_base}-{$widget->number}-custom_id'>添加ID</label>\n";
	$row .= "\t<input type='text' name='widget-{$widget->id_base}[{$widget->number}][custom_id]' id='widget-{$widget->id_base}-{$widget->number}-custom_id' class='widefat' value='{$instance['custom_id']}' />\n";
	$row .= "\t<label for='widget-{$widget->id_base}-{$widget->number}-classes'>CSS类</label>\n";
	$row .= "\t<select name='widget-{$widget->id_base}[{$widget->number}][classes]' id='widget-{$widget->id_base}-{$widget->number}-classes' class='widefat'>";
	foreach( $myclass as $key => $class ) {
		$selected = null;
		if( $class_prefix.$key == $instance['classes'] ) $selected = 'selected = "selected"';
		$row .= "\t<option value='$class_prefix$key' $selected>$class</value>\n";
	}
	$row .= "</select>\n";
	echo $row;
	return $instance;
}
add_filter('widget_form_callback', 'zm_widget_form_extend', 10, 2);
 
function zm_widget_update( $instance, $new_instance ) {
	$instance['classes'] = $new_instance['classes'];
	$instance['custom_id'] = $new_instance['custom_id'];
	return $instance;
}
add_filter( 'widget_update_callback', 'zm_widget_update', 10, 2 );
 
function zm_dynamic_sidebar_params( $params ) {
	global $wp_registered_widgets;
	$widget_id  = $params[0]['widget_id'];
	$widget_obj = $wp_registered_widgets[$widget_id];
	$widget_opt = get_option($widget_obj['callback'][0]->option_name);
	$widget_num = $widget_obj['params'][0]['number'];
 
	if ( isset( $widget_opt[$widget_num]['classes'] ) && !empty( $widget_opt[$widget_num]['classes'] ) )
		$params[0]['before_widget'] = preg_replace( '/class="/', "class=\"{$widget_opt[$widget_num]['classes']} ", $params[0]['before_widget'], 1 );
	if ( isset($widget_opt[$widget_num]['custom_id']) && !empty($widget_opt[$widget_num]['custom_id']) )
		$params[0]['before_widget'] = preg_replace( '/id=".*?"/', "id=\"{$widget_opt[$widget_num]['custom_id']}\"", $params[0]['before_widget'], 1 );
	return $params;
}
add_filter( 'dynamic_sidebar_params', 'zm_dynamic_sidebar_params' );

代码中预设了CSS类名称，可能使用更方便些。

缺点：添加的选项位置在其它小工具选项的上面，需要改进一下。

也可以安装相关插件实现：Widget CSS Classes