mysql 输出乱码

$mysqli = new mysqli("localhost", "user", "password", "database");
$mysqli->set_charset("utf8");

-- 检查数据库字符集
SHOW CREATE DATABASE database_name;

-- 修改数据库字符集
ALTER DATABASE database_name CHARACTER SET utf8 COLLATE utf8_general_ci;

-- 检查表字符集
SHOW CREATE TABLE table_name;

-- 修改表字符集
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_ci;

mysqldump -u user -p database_name --default-character-set=utf8 > backup.sql

mysql -u user -p database_name --default-character-set=utf8 < backup.sql

<?php
$mysqli = new mysqli("localhost", "user", "password", "database");

if ($mysqli->connect_errno) {
    echo "Failed to connect to MySQL: " . $mysqli->connect_error;
    exit();
}

$mysqli->set_charset("utf8");

$sql = "SELECT * FROM table_name";
$result = $mysqli->query($sql);

if ($result) {
    while ($row = $result->fetch_assoc()) {
        echo $row['column_name'] . "<br>";
    }
    $result->free();
} else {
    echo "Query failed: " . $mysqli->error;
}

$mysqli->close();
?>