PHP 创建重用数据库连接函数 mysqli与PDO

代码如下：

有兴趣的可以测试下

摘自于某书

 <? php

  public function dbConnect( $usertype, $connectionType = 'mysqli' ) {
         $host = 'localhost';
         $db = 'phpsols';
         if( $usertype == 'read') {
             $user = 'psread';
             $pwd = '123456';
         } else if ( $usertype == 'write' ) {
             $user = 'pswrite';
             $pwd = '123456';
         } else {
             exit( 'Unrecognized connection type' );
         }
         if( $connectionType == 'mysqli') {
             return new mysqli( $host, $user, $pwd, $db ) or die( 'Cannot open database' );
         } else {
             try {
                 return new PDO( "mysql:host=$host;dbname=$db", $user, $pwd );
             } catch( PDOException $e ) {
                 $e -> getMessage;
                 echo 'Cannot connect to database';
                 exit;
             }
         }
     }

 ?>