使用单例模式pdo连接与多个用户连接

Question

1. 我有一个包含5个用户的数据库，例如hr，pay，misc。我使用单例数据库模式连接并执行对这些数据库用户的查询。
2. 我正在从Config Class访问连接信息，我将连接参数存储为数组。

3. 我想在getInstance方法中更改参数时获取新的连接对象  $ data1 = DB :: getInsatance（＆＃39; common＆＃39;） - ＆gt;查询（＆＃34;从表1中选择*（共同）＆＃34;）;  $ data2 = DB :: getInsatance（＆＃39; misc＆＃39;） - ＆gt;查询（＆＃34;从表2中选择*（在misc中）＆＃34;）;

   但是，无论何时使用单独的用户创建两个实例方法，都不会生成稍后在流中启动的对象

＆＃13;
＆＃13;
<!--
This is my DB class where my pdo parameters will change based on arguement supplied in getInstance() method  --->




<?php
include_once 'Config.php';
class DB {
	private static $_instance = null;
	private $_pdo, $_query, $_error = false, $_results, $_count = 0;
	protected $user;
	private function __construct($user) {
	try {
			$this -> _pdo = new PDO('oci:dbname=//' . Config::get($user.'/host') . '/' . Config::get($user.'/db'), Config::get($user.'/username'), Config::get($user.'/password'));

		} catch (PDOException $e) {
			die($e -> getMessage());
		}
		
		
	}

	public static function getInstance($user) {
		
		if (!isset(self::$_instance)) {
			self::$_instance = new DB($user);
		}
		//return $user;
		return self::$_instance;
	}

	public function query($sql, $params = array()) {
		//echo $sql.'<br>';
		$this -> _error = false;
		if ($this -> _query = $this -> _pdo -> prepare($sql)) {
			$x = 1;
			if (count($params)) {
				foreach ($params as $param) {
					$this -> _query -> bindValue($x, $param);
					$x++;
				}
			}

			if ($this -> _query -> execute()) {
				$this -> _results = $this -> _query -> fetchAll(PDO::FETCH_OBJ);
				foreach ($this ->_results as $result) {
					$this -> _count++;

				}
				//return $this ->_count;
			} else {
				$this -> _error = true;
			}
		}
		return $this;
	}

	public function action($action, $table, $where = array()) {
		if (count($where) === 3) {
			$operators = array('=', '>', '<', '>=', '<=','like');

			$field = $where[0];
			$operator = $where[1];
			$value = $where[2];

			if (in_array($operator, $operators)) {
				$sql = "{$action} FROM {$table} WHERE {$field} {$operator} ?";

				if (!$this -> query($sql, array($value)) -> error()) {
					return $this;
				}
			}
		}
		return false;
	}

	public function get($table, $where) {
		return $this -> action('SELECT *', $table, $where);
	}

	public function delete($table, $where) {
		return $this -> action('DELETE', $table, $where);
	}

	public function getf($keys = array(), $table, $wheres = array(array(),array(),array())) {

		$fields = $wheres[0];
		$qoperator = $wheres[1];
		$values = $wheres[2];
		$operators = array('=', '>', '<', '>=', '<=');
		foreach ($fields as $field) {
			$this -> field = $field;
		}
		foreach ($qoperator as $operator1) {
			$this -> operator = $operator1;

		}
		foreach ($values as $value1) {
			$this -> value = $value1;

		}

		//if (in_array($operator, $operators)) {
		if (count($fields) === count($values)) {
			$sql = "SELECT " . implode(',', $keys) . "FROM {$table} WHERE" . implode('AND', '{$field} {$operator} ?');

		} elseif (count($fields) === 0) {
			$sql = "SELECT " . implode(',', $keys) . "FROM {$table} WHERE" . implode('AND', '{$field} {$operator} ?');

		}
		if (!$this -> query($sql, array($value)) -> error()) {
			return $this;
		}

		//}

		return false;
	}

	public function select($keys, $table, $where) {

		return $this -> getf($keys, $table, $where);
	}

	public function insert($table, $fields = array()) {
		$keys = array_keys($fields);
		$values = '';
		$x = 1;
		foreach ($fields as $field) {
			$values .= '?';
			if ($x < count($fields)) {
				$values .= ', ';
			}
			$x++;
		}

		$sql = "INSERT INTO {$table} (" . implode(',', $keys) . ") VALUES ({$values})";
		if (!$this -> query($sql, $fields) -> error()) {
			return true;

		}
		return false;
	}

	public function update($table, $id, $fields) {
		$set = '';
		$x = 1;

		foreach ($fields as $name => $value) {
			$set .= "{$name} = ?";
			if ($x < count($fields)) {
				$set .= ', ';
			}
			$x++;
		}
		$sql = "UPDATE {$table} SET {$set} WHERE TENDER_ID = {$id}";
		
		if (!$this -> query($sql, $fields) -> error()) {
			return true;
		}
		return false;
	}

	public function results() {
		return $this -> _results;
	}

	public function first() {
		//return $this->results()[0];
		return current($this -> results());
	}

	public function error() {
		return $this -> _error;
	}

	public function count() {
		return $this -> _count;
	}

}
?>
＆＃13;
＆＃13;
＆＃13;

Answer 1

不是在用户更改时设置$ user并添加新连接，而是可以存储连接并仅在不存在时建立新连接：

private function __construct($user) {
    try {
        $this->_pdo = new PDO(
            'oci:dbname=//'.Config::get($user.'/host').'/'.Config::get($user.'/db'), 
            Config::get($user.'/username'), 
            Config::get($user.'/password')
        );
    } catch (PDOException $e) {
        die($e -> getMessage());
    }
}

public static function getInstance($user) {

    if (!empty(self::$_instance[$user])) {
        self::$_instance[$user] = new DB($user);
    }
    return self::$_instance[$user];
}