1.PHP与Mysql扩展（本扩展自 PHP 5.5.0 起已废弃，并在将来会被移除），PHP原生的方式去连接数据库，是面向过程的

      '127.0.0.1:3306',     'db'      => 'test',     'db_user' => 'root',     'db_pwd'  => 'root',     );$mysql_conn = @mysql_connect($mysql_conf['host'], $mysql_conf['db_user'], $mysql_conf['db_pwd']);if (!$mysql_conn) {    die("could not connect to the database:\n" . mysql_error());//诊断连接错误}mysql_query("set names 'utf8'");//编码转化$select_db = mysql_select_db($mysql_conf['db']);if (!$select_db) {    die("could not connect to the db:\n" .  mysql_error());}$sql = "select * from user;";$res = mysql_query($sql);if (!$res) {    die("could get the res:\n" . mysql_error());}while ($row = mysql_fetch_assoc($res)) {    print_r($row);}mysql_close($mysql_conn);?>

2.PHP与Mysqli扩展,面向过程、对象

      '127.0.0.1:3306',     'db'      => 'test',     'db_user' => 'root',     'db_pwd'  => 'joshua317',     );$mysqli = @new mysqli($mysql_conf['host'], $mysql_conf['db_user'], $mysql_conf['db_pwd']);if ($mysqli->connect_errno) {    die("could not connect to the database:\n" . $mysqli->connect_error);//诊断连接错误}$mysqli->query("set names 'utf8';");//编码转化$select_db = $mysqli->select_db($mysql_conf['db']);if (!$select_db) {    die("could not connect to the db:\n" .  $mysqli->error);}$sql = "select uid from user where name = 'joshua';";$res = $mysqli->query($sql);if (!$res) {    die("sql error:\n" . $mysqli->error);} while ($row = $res->fetch_assoc()) {        var_dump($row);    }$res->free();$mysqli->close();?>

3.PHP与PDO扩展,面向过程、对象

      '127.0.0.1:3306',     'db'      => 'test',     'db_user' => 'root',     'db_pwd'  => 'joshua317',     );$pdo = new PDO("mysql:host=" . $mysql_conf['host'] . ";dbname=" . $mysql_conf['db'], $mysql_conf['db_user'], $mysql_conf['db_pwd']);//创建一个pdo对象$pdo->exec("set names 'utf8'");$sql = "select * from user where name = ?";$stmt = $pdo->prepare($sql);$stmt->bindValue(1, 'joshua', PDO::PARAM_STR);$rs = $stmt->execute();if ($rs) {    // PDO::FETCH_ASSOC 关联数组形式    // PDO::FETCH_NUM 数字索引数组形式    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {        var_dump($row);    }}$pdo = null;//关闭连接?>