php连接数据库

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

    define('DB_HOST', 'localhost');
    define('DB_USER', 'root');
    define('DB_PWD', '密码');
    define('DB_NAME', '数据库名');

    $conn = @mysql_connect(DB_HOST, DB_USER, DB_PWD) or die('数据库链接失败：'.mysql_error());

    @mysql_select_db(DB_NAME) or die('数据库错误：'.mysql_error());

    @mysql_query('SET NAMES UTF8') or die('字符集错误：'.mysql_error());
?>

/*****************************
*数据库连接
*****************************/

header("Content-Type:text/html;charset=utf-8");
$conn = @mysql_connect("localhost","root","123456");
if (!$conn){
    die("连接数据库失败：" . mysql_error());
}
mysql_select_db("数据库名", $conn);
//字符转换，读库
mysql_query("set character set 'utf-8'");
//写库
mysql_query("set names 'utf-8'");

mysql_query("create table user
    (id int(10) not null auto_increment,
    name varchar(30) CHARACTER SET utf8 not null DEFAULT '',
    password varchar(30) not null,
    age int(2),
    address varchar(30),
    primary key(id)
    )ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
");

 <?php
 require 'config.php';
 $_pass = sha1($_POST['login_pass']);
 $query = mysql_query("SELECT user,pass FROM user WHERE
 user='{$_POST['login_user']}' AND pass='{$_pass}'") or die('SQL 错误！');
 if (mysql_fetch_array($query, MYSQL_ASSOC)) {
 echo 'true';
 } else {
 echo 'false';
 }
 mysql_close();
 ?>