//封装MySQL单例

class MySQLDB {

private $host;//主机地址

private $port;//端口号

private $user;//用户名

private $pwd;//密码

private $dbname;//数据接名

private $charset;//字符集

private $link;//连接对象

private static $instance;

private function __construct($param) {

$this->initParam($param);

$this->initConnect();

}

private function __clone() {

}

//获取单例

public static function getInstance($param=array()) {

if(!self::$instance instanceof self)

self::$instance=new self($param);

return self::$instance;

}

//初始化参数

private function initParam($param) {

$this->host=$param['host']??'127.0.0.1';

$this->port=$param['port']??'3306';

$this->user=$param['user']??'';

$this->pwd=$param['pwd']??'';

$this->dbname=$param['dbname']??'';

$this->charset=$param['charset']??'utf8';

}

//连接数据库

private function initConnect() {

$this->link=@mysqli_connect($this->host,$this->user,$this->pwd,$this->dbname);

if(mysqli_connect_error()){

echo '数据库连接失败

';

echo '错误信息：'.mysqli_connect_error(),'

';

echo '错误码：'.mysqli_connect_errno(),'

';

exit;

}

mysqli_set_charset($this->link,$this->charset);

}

//执行数据库的增、删、改、查

private function execute($sql) {

if(!$rs=mysqli_query($this->link,$sql)){

echo 'SQL语句执行失败

';

echo '错误信息：'.mysqli_error($this->link),'

';

echo '错误码：'.mysqli_errno($this->link),'

';

echo '错误的SQL语句：'.$sql,'

';

exit;

}

return $rs;

}

/**

*执行增、删、改

[email protected] bool 成功返回true,失败返回false

*/

public function exec($sql) {

$key=substr($sql,0,6);

if(in_array($key,array('insert','update','delete')))

return $this->execute($sql);

else{

echo '非法访问

';

exit;

}

}

//获取自动增长的编号

public function getLastInsertId() {

return mysqli_insert_id($this->link);

}

//执行查询语句

private function query($sql) {

if(substr($sql,0,6)=='select' || substr($sql,0,4)=='show' || substr($sql,0,4)=='desc'){

return $this->execute($sql);

}else{

echo '非法访问

';

exit;

}

}

/**

* 将查询结果改为二维数组

*执行查询语句，返回二维数组

*@$sql string 查询sql语句

[email protected] string assoc|num|both

*/

public function fetchAll($sql,$type='assoc') {

$rs=$this->query($sql);

$type=$this->getType($type);

//$rs代表从一个数据库查询中获取的结果集。

//mysqli_fetch_all 将所有结果行作为关联数组、数字数组或两者都提取

return mysqli_fetch_all($rs,$type);

}

//只有一条记录的时候 应该只返回一条记录

//匹配一维数组

public function fetchRow($sql,$type='assoc') {

$list=$this->fetchAll($sql,$type);

//如果二维数组不为空 则返回第一条数据

if(!empty($list))

return $list[0];

return array();

}

//匹配一行一列

//如 查询数据的条数 只需要一行实际内容就行

public function fetchColumn($sql) {

$list=$this->fetchRow($sql,'num');

if(!empty($list))

return $list[0];

return null;

}

//获取匹配类型

//设置数组键的类型

private function getType($type) {

switch($type){

case 'num':

return MYSQLI_NUM;

case 'both':

return MYSQLI_BOTH;

default:

return MYSQLI_ASSOC;//如果没有传入则默认的ASSOC

}

}

}

//测试

//配置参数

$param=array(

'user'=>'root',

'pwd'=>'root',

'dbname'=>'data'

);

//获取单例

$db=MySQLDB::getInstance($param);

//更新

//$db->exec("update news set title='青草' where id=2");

//插入

/*

if($db->exec("insert into news values (null,'aa','bb',unix_timestamp())"))

echo '编号是：'.$db->getLastInsertId();

*/

//查询

//$list=$db->fetchAll('select * from news','aa');

//$list=$db->fetchRow('select * from news where id=1','aa');

$list=$db->fetchColumn('select count(*) from news');

echo '';

var_dump($list);