WordPress自定义分类小部件报错：无法重复声明cat_count_span()

问题说明 #

为主题创建Consulty_Widget_Categories自定义分类小部件后，同时添加到主侧边栏和页脚侧边栏时触发致命错误：

Fatal error: Cannot redeclare cat_count_span() (previously declared in E:\xampp\htdocs\repo\wp-content\plugins\consulty-core\widgets\categories\class-consulty-cats.php:157) in E:\xampp\htdocs\repo\wp-content\plugins\consulty-core\widgets\categories\class-consulty-cats.php on line 157

该错误由用于给分类文章计数添加span标签的cat_count_span()函数引发。

错误根源 #

问题出在**widget()方法内部定义了命名函数cat_count_span()**：每次小部件实例渲染时，都会尝试重新声明这个函数。当页面存在多个该小部件实例时，PHP不允许重复声明同名函数，因此抛出致命错误。

修复方案 #

有两种可靠的解决方式：

方案1：将函数改为类的静态方法 #

把cat_count_span()定义为类的静态方法，避免重复声明：

// 在类内部添加静态方法
public static function cat_count_span($links) {
    $links = str_replace('</a> (', '<span>(', $links);
    $links = str_replace(')', ')</span></a>', $links);
    return $links;
}

// 在widget()方法中调用过滤器时修改为：
add_filter('wp_list_categories', array(__CLASS__, 'cat_count_span'));

方案2：使用匿名函数替代命名函数 #

直接在add_filter中使用匿名函数，彻底避免重复声明问题：

add_filter('wp_list_categories', function($links) {
    $links = str_replace('</a> (', '<span>(', $links);
    $links = str_replace(')', ')</span></a>', $links);
    return $links;
});

修改后的完整代码 #

<?php
/**
 * Widget API: WP_Widget_Categories class
 *
 * @package WordPress
 * @subpackage Widgets
 * @since 4.4.0
 */

/**
 * Core class used to implement a Categories widget.
 *
 * @since 2.8.0
 *
 * @see WP_Widget
 */
class Consulty_Widget_Categories extends WP_Widget {

    /**
     * Sets up a new Categories widget instance.
     *
     * @since 2.8.0
     */
    public function __construct() {
        $widget_ops = array(
            'classname'                   => 'consulty_widget_categories',
            'description'                 => __( 'A list or dropdown of categories By Consulty.' ),
            'customize_selective_refresh' => true,
            'show_instance_in_rest'       => true,
        );
        parent::__construct( 'consulty_categories', __( 'Consulty Categories' ), $widget_ops );
    }

    /**
     * 静态方法：为分类计数添加span标签
     */
    public static function cat_count_span($links) {
        $links = str_replace('</a> (', '<span>(', $links);
        $links = str_replace(')', ')</span></a>', $links);
        return $links;
    }

    /**
     * Outputs the content for the current Categories widget instance.
     *
     * @since 2.8.0
     * @since 4.2.0 Creates a unique HTML ID for the `select` element
     *              if more than one instance is displayed on the page.
     *
     * @param array $args     Display arguments including 'before_title', 'after_title',
     *                        'before_widget', and 'after_widget'.
     * @param array $instance Settings for the current Categories widget instance.
     */
    public function widget( $args, $instance ) {
        static $first_dropdown = true;

        $default_title = __( 'Categories' );
        $title         = ! empty( $instance['title'] ) ? $instance['title'] : $default_title;

        $title = apply_filters( 'widget_title', $title, $instance, $this->id_base );

        $count        = ! empty( $instance['count'] ) ? '1' : '0';
        $hierarchical = ! empty( $instance['hierarchical'] ) ? '1' : '0';
        $dropdown     = ! empty( $instance['dropdown'] ) ? '1' : '0';

        echo '<div class="sidebar-widget sidebar-categories">';
        echo '<div class="widget-title">';

        if ( $title ) {
            echo $args['before_title'] . $title . $args['after_title'];
        }

        echo '</div>';// End class="widget-title"

        $cat_args = array(
            'orderby'      => 'name',
            'show_count'   => $count,
            'hierarchical' => $hierarchical,
        );

        if ( $dropdown ) {
                printf( '<form action="%s" method="get">', esc_url( home_url() ) );
                $dropdown_id    = ( $first_dropdown ) ? 'cat' : "{$this->id_base}-dropdown-{$this->number}";
                $first_dropdown = false;

                echo '<label class="screen-reader-text" for="' . esc_attr( $dropdown_id ) . '">' . $title . '</label>';

                $cat_args['show_option_none'] = __( 'Select Category' );
                $cat_args['id']               = $dropdown_id;

                wp_dropdown_categories( apply_filters( 'widget_categories_dropdown_args', $cat_args, $instance ) );

                echo '</form>';

                $type_attr = current_theme_supports( 'html5', 'script' ) ? '' : ' type="text/javascript"';
                ?>

                    <script<?php echo $type_attr; ?>>
                        /*
                        <![CDATA[ */
                        (function() {
                            var dropdown = document.getElementById( "<?php echo esc_js( $dropdown_id ); ?>" );
                            function onCatChange() {
                                if ( dropdown.options[ dropdown.selectedIndex ].value > 0 ) {
                                    dropdown.parentNode.submit();
                                }
                            }
                            dropdown.onchange = onCatChange;
                        })();
                        /* ]]> */
                    </script>

                    <?php
        } else {
                $format = current_theme_supports( 'html5', 'navigation-widgets' ) ? 'html5' : 'xhtml';

                $format = apply_filters( 'navigation_widgets_format', $format );

                if ( 'html5' === $format ) {
                    $title      = trim( strip_tags( $title ) );
                    $aria_label = $title ? $title : $default_title;
                    echo '<nav aria-label="' . esc_attr( $aria_label ) . '">';
                }
                ?>
                <div class="widget-content">
                    <ul class="categories-list clearfix">
                        <?php
                            $cat_args['title_li'] = '';

                            // 使用类静态方法作为过滤器
                            add_filter('wp_list_categories', array(__CLASS__, 'cat_count_span'));

                            wp_list_categories( apply_filters( 'widget_categories_args', $cat_args, $instance ) );
                            ?>
                    </ul>
                </div><!-- /.widget-content -->
                
                <?php
                        if ( 'html5' === $format ) {
                            echo '</nav>';
                        }
            }

        echo '</div>';// End class="sidebar-widget sidebar-categories"

    }

    /**
     * Handles updating settings for the current Categories widget instance.
     *
     * @since 2.8.0
     *
     * @param array $new_instance New settings for this instance as input by the user via
     *                            WP_Widget::form().
     * @param array $old_instance Old settings for this instance.
     * @return array Updated settings to save.
     */
    public function update( $new_instance, $old_instance ) {
        $instance                 = $old_instance;
        $instance['title']        = sanitize_text_field( $new_instance['title'] );
        $instance['count']        = ! empty( $new_instance['count'] ) ? 1 : 0;
        $instance['hierarchical'] = ! empty( $new_instance['hierarchical'] ) ? 1 : 0;
        $instance['dropdown']     = ! empty( $new_instance['dropdown'] ) ? 1 : 0;

        return $instance;
    }

    /**
     * Outputs the settings form for the Categories widget.
     *
     * @since 2.8.0
     *
     * @param array $instance Current settings.
     */
    public function form( $instance ) {
        $instance     = wp_parse_args( (array) $instance, array( 'title' => '' ) );
        $count        = isset( $instance['count'] ) ? (bool) $instance['count'] : false;
        $hierarchical = isset( $instance['hierarchical'] ) ? (bool) $instance['hierarchical'] : false;
        $dropdown     = isset( $instance['dropdown'] ) ? (bool) $instance['dropdown'] : false;
        ?>
        <p>
            <label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
            <input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>"
                name="<?php echo $this->get_field_name( 'title' ); ?>" type="text"
                value="<?php echo esc_attr( $instance['title'] ); ?>" />
        </p>

        <p>
            <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'dropdown' ); ?>"
                name="<?php echo $this->get_field_name( 'dropdown' ); ?>" <?php checked( $dropdown ); ?> />
            <label for="<?php echo $this->get_field_id( 'dropdown' ); ?>"><?php _e( 'Display as dropdown' ); ?></label>
            <br />

            <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'count' ); ?>"
                name="<?php echo $this->get_field_name( 'count' ); ?>" <?php checked( $count ); ?> />
            <label for="<?php echo $this->get_field_id( 'count' ); ?>"><?php _e( 'Show post counts' ); ?></label>
            <br />

            <input type="checkbox" class="checkbox" id="<?php echo $this->get_field_id( 'hierarchical' ); ?>"
                name="<?php echo $this->get_field_name( 'hierarchical' ); ?>" <?php checked( $hierarchical ); ?> />
            <label for="<?php echo $this->get_field_id( 'hierarchical' ); ?>"><?php _e( 'Show hierarchy' ); ?></label>
        </p>
        <?php
    }

}

// Register and load the widget
function consulty_register_custom_cat() {
    register_widget( 'Consulty_Widget_Categories' );
}
add_action( 'widgets_init', 'consulty_register_custom_cat' );

内容的提问来源于stack exchange，提问作者Hatem Frere