请问我是PDO的新手,也是PHP的新手。我目前正在开发一个涉及许多数据库连接的项目:MySQL,MSSQL和Oracle。所以我使用下面的类,PDO,用于我的连接。类代码如下。
class db {
private static $objInstance;
/*
* Class Constructor - Create a new database connection if one doesn't exist
* Set to private so no-one can create a new instance via ' = new DB();'
*/
private function __construct() {}
/*
* Like the constructor, we make __clone private so nobody can clone the instance
*/
private function __clone() {}
/*
* Returns DB instance or create initial connection
* @param
* @return $objInstance;
*/
public static function getDB($DBtype, $DBindex) {
include('vars.inc.php');
if (!self::$objInstance){
$DBid = $DBindex - 1;
switch ($DBtype){
case "mysql":
self::$objInstance = new PDO("mysql:host=".$dbvars[$DBid][0].";dbname=".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
case "mssql":
self::$objInstance = new PDO("odbc:Driver={SQL Server};Server=".$dbvars[$DBid][0].";Database=".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
case "oci";
self::$objInstance = new PDO("oci:dbname=//".$dbvars[$DBid][0].":".$dbvars[$DBid][4]."/".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
// Add other case(s) here if another RDBMS (Relational Database Management system) is used
default:
break;
}
self::$objInstance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
return self::$objInstance;
}
private static $objInstance;
/*
* Class Constructor - Create a new database connection if one doesn't exist
* Set to private so no-one can create a new instance via ' = new DB();'
*/
private function __construct() {}
/*
* Like the constructor, we make __clone private so nobody can clone the instance
*/
private function __clone() {}
/*
* Returns DB instance or create initial connection
* @param
* @return $objInstance;
*/
public static function getDB($DBtype, $DBindex) {
include('vars.inc.php');
if (!self::$objInstance){
$DBid = $DBindex - 1;
switch ($DBtype){
case "mysql":
self::$objInstance = new PDO("mysql:host=".$dbvars[$DBid][0].";dbname=".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
case "mssql":
self::$objInstance = new PDO("odbc:Driver={SQL Server};Server=".$dbvars[$DBid][0].";Database=".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
case "oci";
self::$objInstance = new PDO("oci:dbname=//".$dbvars[$DBid][0].":".$dbvars[$DBid][4]."/".$dbvars[$DBid][1], $dbvars[$DBid][2], $dbvars[$DBid][3]);
break;
// Add other case(s) here if another RDBMS (Relational Database Management system) is used
default:
break;
}
self::$objInstance-> setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
}
return self::$objInstance;
}
这里是类所需的vars包含文件,我使用了数组cos,我觉得这样,随着时间的推移,非程序员可以轻松地将新数据库添加到vars文件中。当然,在这里,我已经更改了var文件值。
define('DB_SERVER', 'localhost'); define('DB_NAME', 'db1name'); define('DB_USER', 'root'); define('DB_PASSWORD', 'rootpass'); define('DB_PORT', ''); define('DB2_SERVER', 'xxx.xxx.xx.xxx'); define('DB2_NAME', 'db2name'); define('DB2_USER', 'root2'); define('DB2_PASSWORD', 'rootpass2'); define('DB2_PORT', ''); define('DB3_SERVER', 'xx.xxx.xxx.xxx'); define('DB3_NAME', db3name'); define('DB3_USER', 'root3'); define('DB3_PASSWORD', 'rootpass3'); define('DB3_PORT', ''); define('DB4_SERVER', 'xxx.xx.xxx.xx'); define('DB4_NAME', 'oracledb'); define('DB4_USER', 'root4'); define('DB4_PASSWORD', 'rootpass4'); define('DB4_PORT', '1521'); $dbvars = array( array(DB_SERVER, DB_NAME , DB_USER, DB_PASSWORD, DB_PORT), array(DB2_SERVER, DB2_NAME , DB2_USER, DB2_PASSWORD, DB2_PORT), array(DB3_SERVER, DB3_NAME , DB3_USER, DB3_PASSWORD, DB3_PORT), array(DB4_SERVER, DB4_NAME , DB4_USER, DB4_PASSWORD, DB4_PORT) );
现在的问题是,每当我连接到一个数据库并尝试在另一个数据库上运行查询时,PDO就会记住旧数据库。但如果我独立运行任何查询,一切都很好。有人可以帮忙解决这个问题,还是建议一个更好的方法? :(
E.g。
}
include('./includes/db.class.php');
try {
$result = DB::getDB("mysql", 3)->query("SELECT myrow FROM mytable");
在这种情况下,PDO将继续检查用于TABLE yourtable的DATABASE db1name,而不是检查DATABASE db3name。所以PDO会抛出一个错误: foreach($result as $row){
print $row['myrow'].'<br />';
}
}catch(PDOException $e){
echo $e->getMessage();
}
echo "<br />Then<br /><hr /><br />";
try {
$result = DB::getDB("mysql", 1)->query("SELECT yourrow FROM yourtable");
foreach($result as $row){
print $row['yourrow'].'<br />' ;
}
}catch(PDOException $e){
echo $e->getMessage();
}
SQLSTATE [42S02]:未找到基表或视图:1146表'db1name.yourtable'不存在
答案 0 :(得分:3)
您将其设置为单身人士。因此,您对Db::getDB
的下一次调用将返回原始实例。如果要在脚本持续时间内缓存实例,请将$objInstance
更改为数组,然后执行以下操作:
if (!self::$objInstance){
待办事项
$signature = $DBtype . $DBindex;
if (!isset(self::$objInstances[$signature])) {
当然你也需要改变作业线和回归线,但我觉得你明白了......
答案 1 :(得分:2)
由于以下行,您的getDB函数似乎只会连接一次:
if (!self::$objInstance){
因此,当您第一次执行它时,它将连接,但在所有后续调用中,逻辑将被忽略。
我建议在您的类中添加另一个属性,用于存储当前的DBType并将条件更改为:
if (!self::$objInstance || $DBtype != self::$dbtype){
您必须在switch语句的每个case中设置$ dbtype。