php打开乱码

// 设置文件编码为UTF-8
header('Content-Type: text/html; charset=utf-8');

// 读取文件时指定编码
$content = file_get_contents('filename.txt', FILE_TEXT);
$content = mb_convert_encoding($content, 'UTF-8', 'auto');

// 写入文件时指定编码
file_put_contents('filename.txt', $content, LOCK_EX);

// 连接数据库时指定编码
$mysqli = new mysqli('host', 'user', 'password', 'database');
$mysqli->set_charset('utf8mb4');

// 查询数据
$result = $mysqli->query('SELECT * FROM table_name');
while ($row = $result->fetch_assoc()) {
    // 处理数据
}

// 设置HTTP头指定网页编码
header('Content-Type: text/html; charset=utf-8');