单例模式实现mysql数据库的增删查改

  1. <?php
  2. // 单例模式连接数据库 应用程序跟设计库交互
  3. namespace app\chloe;
  5. use pdo;
  7. interface idbBase
  8. {
  9.     // 数据库连接curd
  10.     static function insert($db, $data);
  11.     static function select($db, $where = []);
  12.     static function update($db, $where = []);
  13.     static function delete($db, $data, $where = []);
  15.     // 数据库连接
  16.     static function doconnect($dsn, $user, $password);
  17. }
  23. // 单例模式连接数据库
  24. abstract class adb implements idbBase
  25. {
  26.     private static $_instance;
  28.     private function __construct()
  29.     {
  30.     }
  32.     private function __clone()
  33.     {
  34.     }
  37.     static function doconnect($dsn, $user, $password)
  38.     {
  39.         // 创建adb类的唯一实例 获取唯一的pdo对象
  40.         if (is_null(self::$_instance)) {
  41.             echo 2;
  42.             self::$_instance = new pdo($dsn, $user, $password);
  43.         }
  44.         return self::$_instance;
  45.     }
  46. }
  49. //工作类 
  50. class DB extends adb
  51. {
  52.     // 数据库连接curd
  53.     static function insert($db, $data)
  54.     {
  55.     }
  56.     static function select($db, $where = ['uid' => 1])
  57.     {
  58.         foreach ($where as $k => $v) {
  59.             $sql = $k . ' > ' . $v;
  60.         }
  61.         return $db->query("SELECT * FROM `mj_user` WHERE " . $sql . " LIMIT 3;")->fetchAll(PDO::FETCH_ASSOC);
  62.     }
  63.     static function update($db, $where = [])
  64.     {
  65.     }
  66.     static function delete($db, $data, $where = [])
  67.     {
  68.     }
  69. }
  70. //客户端代码
  71. $config = [
  72.     'type' => $type ?? 'mysql',
  73.     'host' => $host ?? 'localhost',
  74.     'dbname' => $dbname ?? 'phpcn',
  75.     'username' => $username ?? 'root',
  76.     'password' => $password ?? '',
  77.     'port' => $port ?? '3308',
  78.     'charset' => $charset ?? 'utf8'
  79. ];
  80. extract($config);
  81. $dsn = sprintf('%s:host=%s;port=%s;charset=%s;dbname=%s', $type, $host, $port, $charset, $dbname);
  83. $pdo = DB::doconnect($dsn, $username, $password);
  84. // var_dump(DB::select($pdo));
  87. // 检查是否获取到pdo唯一实例
  88. for ($i = 0; $i < 10; $i++) {
  89.     adb::doconnect($dsn, $username, $password);
  90. }