PHP连接数据库实例详解 PHP怎么连接数据库

$con = mysql_connect("localhost","root","");
if (!$con)
{
die('Could not connect: ' . mysql_error());
}
mysql_close($con);
?>

$mysqli = new mysqli('localhost','root','','volunteer');
if (mysqli_connect_errno()){
die('Unable to connect!'). mysqli_connect_error();
}
?>

$db = new PDO('mysql:host=localhost;dbname=test', 'root', '');
try {
foreach ($db->query('select * from user') as $row){
print_r($row);
}
$db = null; //关闭数据库
} catch (PDOException $e) {
echo $e->getMessage();
}
?>

require_once './adodb5/adodb.inc.php'
$conn = &ADONewConnection('mysql');
$conn->connect('localhost','root','','test');
$conn->Execute("set names utf8");
$res = $conn->Execute("select * from user");
if (!$res){
echo $conn->ErrorMsg();
}else{
var_dump($res);
}
?>

//------------------------------------------------------------------------------------------
// ※Database() 构造函数，数据库初始参数
// ※Select() 查询
// ※GetRows() 返回查询的记录总数
// ※Insert() 插入记录
// ※Update() 更新
// ※Delete() 删除
// ※Halt() 中断并显示错误信息*/
//------------------------------------------------------------------------------------------
define("DATABASETYPE", "1"); //定义数据库类型:1为MySql;2为SQL Server;3为Oracle;4为Odbc
define("SERVER", "localhost"); //Host name or IP address of the database server
define("DATABASE", "dbName"); //要连接的数据库名
define("USER", "tableName"); //用于连接数据库的用户名
define("PASSWORD", "paswd"); //用于连接数据库的密码

class Database {
var $dbLink; //连接句柄
var $result; //查询句柄
var $insId; //Insert()成功返回AUTO_INCREMENT列的值
var $rows; //返回数据数组
var $numRows; //返回数据数目
var $dbHost, $dbUser, $userPassword, $database;
var $dbType = DATABASETYPE;
var $msgFlag = "yes"; //yes:show the Mysql message ; no: die by show "Halted."

function Database($dbHost = SERVER, $dbUser = USER, $userPassword = PASSWORD, $database = DATABASE) {
switch ($this->dbType) {
case 1:
$this->dbLink = @mysql_pconnect($dbHost, $dbUser, $userPassword); // or die("Can't Connect to Remote Host!");
@mysql_select_db($database, $this->dbLink); // or die ("Can't Connect to Remote Host!");
break;
case 2:
break;
}
return true;
}

/* SQL:Select() 返回为false无结果 */

function Select($table, $columns, $condition = 1) {
$sql = "select $columns from $table where $condition ";
$this->result = @mysql_query($sql, $this->dbLink);
unset($this->rows);
if ($this->result) {
$i = 0;
if (!($this->rows = array("$i" => @mysql_fetch_array($this->result))))
return false;
if (($this->numRows = @mysql_num_rows($this->result)) == 0)
return false;
while ($tempRows = @mysql_fetch_array($this->result)) {
array_push($this->rows, $tempRows);
}
} else {
$this->Halt($sql);
return false;
}
return true;
}

/* SQL:GetRows() 返回查询的记录总数 */

function GetRows($table, $condition = 1) {
$sql = "select count(1) as count from $table where $condition";
$this->result = @mysql_query($sql, $this->dbLink);
if ($this->result) {
$temp = @mysql_fetch_array($this->result);
$this->numRows = $temp[count];
} else {
$this->Halt($sql);
return false;
}
return $this->numRows;
}

/* SQL:Insert() */

function Insert($table, $columns, $values) {
$sql = "insert into $table ($columns) values ($values)";
$this->result = @mysql_query($sql, $this->dbLink);
if ($this->result)
$this->insId = @mysql_insert_id($this->dbLink);
else {
$this->Halt($sql);
return false;
}
return true;
}

/* SQL:Update() */

function Update($table, $setings, $condition) {
$sql = "update $table set $setings where $condition";
$this->result = @mysql_query($sql, $this->dbLink);
if ($this->result)
$this->numRows = @mysql_affected_rows($this->result);
else {
$this->Halt($sql);
return false;
}
return true;
}

/* SQL:Delete */

function Delete($table, $condition) {
$sql = "delete from $table where $condition";
$this->result = @mysql_query($sql, $this->dbLink);
if ($this->result)
$this->numRows = @mysql_affected_rows($this->result);
else {
$this->Halt($sql);
return false;
}
return true;
}

/* Halt():error message */

function Halt($msg) {
if ($this->msgFlag == "yes") {
printf("Database Query Error:%s
n", $msg);
printf("MySql Error:%s
n", mysql_error());
}else
echo "include/error.htm'>"; //自定一个出错提示文件
return false;
}
}

switch ($db->dbType) {
case 1:
@mysql_close();
break;
case 2:
break;
}
$db = new Database();
?>