如何将非英语字符串（如波斯语）插入Wordpress数据库中的tabale？当我插入波斯字符串时，它显示为"??????" 表格中的字符？代码如下：

-正在创建表：

function fjn_add_polls_table_to_db(){
    global $wpdb;
    $polls_table = $wpdb->prefix. \'polls\';
    if( $wpdb->get_var( "SHOW TABLES LIKE \'{$polls_table}\'" ) != $polls_table ){
        $query =
            "CREATE TABLE {$polls_table} (
            poll_id BIGINT(20) UNSIGNED ZEROFILL AUTO_INCREMENT PRIMARY KEY,
            title VARCHAR(128),
            author_id TINYINT(4) ,
            all_votes BIGINT(20) DEFAULT 0
            );";
        require_once( ABSPATH. \'wp-admin/includes/upgrade.php\' );
        dbDelta( $query );
    }
}
register_activation_hook(__FILE__, \'fjn_add_polls_table_to_db\');

function add_records_to_db(){
    global $wpdb;
    global $post;
    $pid=get_the_ID();
    $ptitle=get_the_title();
    $aid=$post->post_author;
    $wpdb->insert( 
    \'wp_polls\', 
    array( 
        \'poll_id\' => $pid , 
        \'title\' => $ptitle,
        \'author_id\' => $aid,
        \'all_votes\' => "",
    ), 
    array( 
        \'%d\', 
        \'%s\',
        \'%d\',
        \'%d\'
    ) 
);
}
add_action( \'publish_poll\', \'add_records_to_db\');