array_merge()：预期参数 1 是一个数组，在答案

【问题标题】：array_merge(): Expected parameter 1 to be an array, null given inarray_merge()：预期参数 1 是一个数组，在
【发布时间】：2021-01-10 10:57:47
【问题描述】：

警告：array_merge()：预期参数 1 是一个数组，在 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/data-stores/class-wc-product-data-store 中给出 null -cpt.php 在第 1263 行

警告：count()：参数必须是数组或对象，在 /home/sitename/public_html/wp-content/plugins/woocommerce/includes/data-stores/class-wc-product-data- 中实现 Countable store-cpt.php 在第 1296 行

/**
     * Builds the related posts query.
     *
     * @since 3.0.0
     *
     * @param array $cats_array  List of categories IDs.
     * @param array $tags_array  List of tags IDs.
     * @param array $exclude_ids Excluded IDs.
     * @param int   $limit       Limit of results.
     *
     * @return array
     */
    public function get_related_products_query( $cats_array, $tags_array, $exclude_ids, $limit ) {
        global $wpdb;

        $include_term_ids            = array_merge( $cats_array, $tags_array );
        $exclude_term_ids            = array();
        $product_visibility_term_ids = wc_get_product_visibility_term_ids();

        if ( $product_visibility_term_ids['exclude-from-catalog'] ) {
            $exclude_term_ids[] = $product_visibility_term_ids['exclude-from-catalog'];
        }

        if ( 'yes' === get_option( 'woocommerce_hide_out_of_stock_items' ) && $product_visibility_term_ids['outofstock'] ) {
            $exclude_term_ids[] = $product_visibility_term_ids['outofstock'];
        }

        $query = array(
            'fields' => "
                SELECT DISTINCT ID FROM {$wpdb->posts} p
            ",
            'join'   => '',
            'where'  => "
                WHERE 1=1
                AND p.post_status = 'publish'
                AND p.post_type = 'product'

            ",
            'limits' => '
                LIMIT ' . absint( $limit ) . '
            ',
        );

        if ( count( $exclude_term_ids ) ) {
            $query['join']  .= " LEFT JOIN ( SELECT object_id FROM {$wpdb->term_relationships} WHERE term_taxonomy_id IN ( " . implode( ',', array_map( 'absint', $exclude_term_ids ) ) . ' ) ) AS exclude_join ON exclude_join.object_id = p.ID';
            $query['where'] .= ' AND exclude_join.object_id IS NULL';
        }

        if ( count( $include_term_ids ) ) {
            $query['join'] .= " INNER JOIN ( SELECT object_id FROM {$wpdb->term_relationships} INNER JOIN {$wpdb->term_taxonomy} using( term_taxonomy_id ) WHERE term_id IN ( " . implode( ',', array_map( 'absint', $include_term_ids ) ) . ' ) ) AS include_join ON include_join.object_id = p.ID';
        }

        if ( count( $exclude_ids ) ) {
            $query['where'] .= ' AND p.ID NOT IN ( ' . implode( ',', array_map( 'absint', $exclude_ids ) ) . ' )';
        }

        return $query;
    }

【问题讨论】：

根据报错信息，$cats_array 为空。既然是函数的输入，那调用函数的代码肯定有问题。
在合并数组之前必须检查数组是否为空

标签： php arrays wordpress woocommerce

【解决方案1】：

所以为了避免这个错误信息，测试你的变量是否是数组，如果没有设置你的变量是空数组：

if( !is_array( $cat_array ) ){
   // create an empty array to avoid error message
   $cat_array = [];
}

if( !is_array( $tags_array ) ){
   // create an empty array to avoid error message
   $tags_array = [];
}

$include_term_ids            = array_merge( $cats_array, $tags_array );

【讨论】：