1，最简单的方式-mysql（面向过程）
<?php$con = mysql_connect("localhost","root","password");$select_db = mysql_select_db('test');if (!$select_db) {    die("could not connect to the db:\n" .  mysql_error());

}//查询代码$sql = "select * from db_table";$res = mysql_query($sql);if (!$res) {    die("could get the res:\n" . mysql_error());

}while ($row = mysql_fetch_assoc($res)) {    print_r($row);

}//查询代码

//关闭数据库连接mysql_close($con);?>
2，新的方式-mysqli（面向过程）
$mysql_server_name = 'localhost'; //改成自己的mysql数据库服务器$mysql_username = 'root'; //改成自己的mysql数据库用户名$mysql_password = 'password'; //改成自己的mysql数据库密码$mysql_database = 'test'; //改成自己的mysql数据库名$conn=mysqli_connect($mysql_server_name,$mysql_username,$mysql_password,$mysql_database); //连接数据库

//连接数据库错误提示if (mysqli_connect_errno($conn)) {

    die("连接 MySQL 失败: " . mysqli_connect_error());

}mysqli_query($conn,"set names utf8"); //数据库编码格式

// mysqli_set_charset($conn,"utf8");//设置默认客户端字符集。

// mysqli_select_db($conn,$mysql_database); //更改连接的默认数据库

//查询代码$sql = “select * from db_table”;$query = mysqli_query($conn,$sql);while($row = mysqli_fetch_array($query)){    echo $row['title'];

}//查询代码

// 释放结果集+关闭MySQL数据库连接mysqli_free_result($result);mysqli_close($conn);
3，常用方式-mysqli（面向对象）

//连接数据库方式1$conn = new mysqli('localhost', 'root', 'password', 'test');//连接数据库方式2

// $conn = new mysqli();

// $conn -> connect('localhost', 'root', 'password', 'test');

//check connection (检查PHP是否连接上MYSQL)if ($conn -> connect_errno) {    printf("Connect failed: %s\n", $conn->connect_error);    exit();

}//查询代码$sql = “select * from db_table”;$query = $conn->query($sql);while($row = $query->fetch_array()){    echo $row['title'];

}//查询代码

//释放结果集+关闭MySQL连接$query1 -> free_result();$conn -> close();
4，PDO连接MySQL数据库
<?php$db = new PDO('mysql:host=localhost;dbname=test', 'root', 'password');try {    foreach ($db->query('select * from db_table') as $row){    print_r($row);

    }    $db = null; //关闭数据库} catch (PDOException $e) {    echo $e->getMessage();

}?>
5，ADODB连接MySQL数据库
<?php

//安装驱动-引入类即可

require_once './adodb5/adodb.inc.php';

$conn = &ADONewConnection('mysql');

$conn->connect('localhost','root','password','test');

$conn->Execute("set names utf8");

//查询代码

$res = $conn->Execute("select * from db_table");

if (!$res){

    echo $conn->ErrorMsg();

}else{

    var_dump($res);

}

?>

//关闭连接

$conn->close();

6总结-关闭mysql数据库的连接方法

MySQL - 面向过程

    mysql_close($conn);

MySQLi - 面向过程

    mysqli_close($conn);

MySQLi - 面向对象

    $conn->close();

PDO

    $conn = null;

ADODB

    $conn->close();

或

    $conn->free();