php 单例模式的类,用单例模式来设计一个PHP数据库类
class nmdb
{
private $link;
static private $_instance;
// 連接數(shù)據(jù)庫
private function __construct($host, $username, $password)
{
$this->link = mysql_connect($host, $username, $password);
$this->query("SET NAMES 'utf8'", $this->link);
//echo mysql_errno($this->link) . ": " . mysql_error($link). "n";
//var_dump($this->link);
return $this->link;
}
private function __clone(){}
public static function get_class_nmdb($host, $username, $password)
{
//$connector = new nmdb($host, $username, $password);
//return $connector;
if( FALSE == (self::$_instance instanceof self) )
{
self::$_instance = new self($host, $username, $password);
}
return self::$_instance;
}
// 連接數(shù)據(jù)表
public function select_db($database)
{
$this->result = mysql_select_db($database);
return $this->result;
}
// 執(zhí)行SQL語句
public function query($query)
{
return $this->result = mysql_query($query, $this->link);
}
// 將結(jié)果集保存為數(shù)組
public function fetch_array($fetch_array)
{
return $this->result = mysql_fetch_array($fetch_array, MYSQL_ASSOC);
}
// 獲得記錄數(shù)目
public function num_rows($query)
{
return $this->result = mysql_num_rows($query);
}
// 關(guān)閉數(shù)據(jù)庫連接
public function close()
{
return $this->result = mysql_close($this->link);
}
}
?>
這個類的使用如下：
$connector = nmdb::get_class_nmdb($host, $username, $password);
$connector -> select_db($database);
下面的類也可以參考下：
/*
* mysql 單例
*/
class mysql{
private $host ='localhost'; //數(shù)據(jù)庫主機
private $user = 'root'; //數(shù)據(jù)庫用戶名
private $pwd = ''; //數(shù)據(jù)庫用戶名密碼
private $database = 'imoro_imoro'; //數(shù)據(jù)庫名
private $charset = 'utf8'; //數(shù)據(jù)庫編碼，GBK,UTF8,gb2312
private $link; //數(shù)據(jù)庫連接標識;
private $rows; //查詢獲取的多行數(shù)組
static $_instance; //存儲對象
/**
* 構(gòu)造函數(shù)
* 私有
*/
private function __construct($pconnect = false) {
if (!$pconnect) {
$this->link = @ mysql_connect($this->host, $this->user, $this->pwd) or $this->err();
} else {
$this->link = @ mysql_pconnect($this->host, $this->user, $this->pwd) or $this->err();
}
mysql_select_db($this->database) or $this->err();
$this->query("SET NAMES '{$this->charset}'", $this->link);
return $this->link;
}
/**
* 防止被克隆
*
*/
private function __clone(){}
public static function getInstance($pconnect = false){
if(FALSE == (self::$_instance instanceof self)){
self::$_instance = new self($pconnect);
}
return self::$_instance;
}
/**
* 查詢
*/
public function query($sql, $link = '') {
$this->result = mysql_query($sql, $this->link) or $this->err($sql);
return $this->result;
}
/**
* 單行記錄
*/
public function getRow($sql, $type = MYSQL_ASSOC) {
$result = $this->query($sql);
return @ mysql_fetch_array($result, $type);
}
/**
* 多行記錄
*/
public function getRows($sql, $type = MYSQL_ASSOC) {
$result = $this->query($sql);
while ($row = @ mysql_fetch_array($result, $type)) {
$this->rows[] = $row;
}
return $this->rows;
}
/**
* 錯誤信息輸出
*/
protected function err($sql = null) {
//這里輸出錯誤信息
echo 'error';
exit();
}
}
//用例
$db = mysql::getInstance();
$db2 = mysql::getInstance();
$data = $db->getRows('select * from blog');
//print_r($data);
//判斷兩個對象是否相等
if($db === $db2){
echo 'true';
}
?>
總結(jié)
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