用单例模式来设计一个PHP数据库类

来源：互联网发布：删除表数据 sql 编辑：程序博客网时间：2024/05/11 14:29

<?phpclass nmdb {private $link;static private $_instance;// 连接数据库private function __construct($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;    }// 连接数据表public function select_db($database){$this->result = mysql_select_db($database);return $this->result;}// 执行SQL语句public function query($query){return $this->result = mysql_query($query, $this->link);}// 将结果集保存为数组public function fetch_array($fetch_array){return $this->result = mysql_fetch_array($fetch_array, MYSQL_ASSOC);}// 获得记录数目public function num_rows($query){return $this->result = mysql_num_rows($query);}// 关闭数据库连接public function close(){return $this->result = mysql_close($this->link);}}?>

这个类的使用如下：

$connector = nmdb::get_class_nmdb($host, $username, $password);$connector -> select_db($database);

下面的类也可以参考下：

<?php/** mysql 单例*/class mysql{    private $host    ='localhost'; //数据库主机    private $user     = 'root'; //数据库用户名    private $pwd     = ''; //数据库用户名密码    private $database = 'imoro_imoro'; //数据库名    private $charset = 'utf8'; //数据库编码，GBK,UTF8,gb2312    private $link;             //数据库连接标识;    private $rows;             //查询获取的多行数组    static $_instance; //存储对象    /**     * 构造函数     * 私有     */    private function __construct($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;    }    /**     * 查询     */    public function query($sql, $link = '') {        $this->result = mysql_query($sql, $this->link) or $this->err($sql);        return $this->result;    }    /**     * 单行记录     */    public function getRow($sql, $type = MYSQL_ASSOC) {        $result = $this->query($sql);        return @ mysql_fetch_array($result, $type);    }    /**     * 多行记录     */    public function getRows($sql, $type = MYSQL_ASSOC) {        $result = $this->query($sql);        while ($row = @ mysql_fetch_array($result, $type)) {            $this->rows[] = $row;        }        return $this->rows;    }    /**     * 错误信息输出     */    protected function err($sql = null) {        //这里输出错误信息        echo 'error';        exit();    }}//用例$db = mysql::getInstance();$db2 = mysql::getInstance();$data = $db->getRows('select * from blog');//print_r($data);//判断两个对象是否相等if($db === $db2){    echo 'true';}?>

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