php中文保存数据库乱码怎么办

CREATE DATABASE dbname CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

CREATE TABLE tablename (    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,    name VARCHAR(30) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci,    age INT(3)) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;

header('Content-Type: text/html; charset=utf-8');

default_charset = "utf-8"

$dsn = "mysql:host=localhost;dbname=dbname;charset=utf8mb4";$dbh = new PDO($dsn, $user, $password);

$mysqli = new mysqli("localhost", "user", "password", "dbname");mysqli_set_charset($mysqli, "utf8mb4");

$str = "你好";$str = iconv('gbk', 'utf-8', $str);//或$str = mb_convert_encoding($str, 'utf-8', 'gbk');