PHP的单例模式代码

 dbHost = $conf['dbHost']; $this -> dbUser = $conf['dbUser']; $this -> dbName = $conf['dbName']; $this -> dbPass = $conf['dbPass']; $this -> charset = $conf['charset']; $this->connectDb(); $this->selectDb(); $this->setCharset(); } //私有的克隆方法 private function __clone(){} public static function getInstance($conf){ if(!self::$obj instanceof self){ self::$obj = new self($conf); } return self::$obj; } //私有的连接数据库方法 private function connectDb(){ if(!@mysql_connect($this->dbHost,$this->dbUser,$this->dbPass)){ die('PHP连接mysql出错'); } } //私有的选择数据库方法 private function selectDb(){ if(!mysql_select_db($this->dbName)){ die('连接数据库出错'); } } //私有的选择字符集方法 private function setCharset(){ mysql_set_charset($this->charset); } //将sql语句分为两类，返回结果集和返回布尔值 //返回布尔值 public function exec($sql){ //将sql语句转化为小写 $sql = strtolower($sql); //判断是否为select语句 if(substr($sql,0,6) == 'select'){ die('不能执行select语句'); } return mysql_query($sql); } //私有的执行select语句（结果集不能直接展示给前端，得经过处理返给对象） private function query($sql){ //将sql语句转化为小写 $sql = strtolower($sql); //判断是否为select语句 if(substr($sql,0,6) != 'select'){ die('只能执行select语句'); } return mysql_query($sql); } //将查询到的结果集返回给前端(返回一条) public function fetchOne($sql,$type=3){ $res = $this ->query($sql); $types = array( 1 => MYSQL_NUM, 2 => MYSQL_ASSOC, 3 => MYSQL_BOTH, ); //返回一条记录 return mysql_fetch_array($res,$types[$type]); } //将查询到的结果集返回给前端(返回多条) public function fetchAll($sql,$type=2){ $res = $this ->query($sql); $types = array( 1 => MYSQL_NUM, 2 => MYSQL_ASSOC, 3 => MYSQL_BOTH, ); while($row = mysql_fetch_array($res,$types[$type])){ $arr[] = $row; } return $arr; } //公共的获取记录数的方法 public function getCount($sql){ $res= $this ->query($sql); return mysql_num_rows($res); } }

 'localhost', 'dbUser' => 'root', 'dbPass' => 'root', 'dbName' => 'test', 'charset' => 'utf8', ); $db = Db::getInstance($arr); $sql = "select * from account where id = 100;"; var_dump($db->fetchOne($sql,2));