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<?php
/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <fabien@symfony.com>
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code.
*/
namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;
/**
* Session handler using a PDO connection to read and write data.
*
* Session data is a binary string that can contain non-printable characters like the null byte.
* For this reason this handler base64 encodes the data to be able to save it in a character column.
*
* This version of the PdoSessionHandler does NOT implement locking. So concurrent requests to the
* same session can result in data loss due to race conditions.
*
* @author Fabien Potencier <fabien@symfony.com>
* @author Michael Williams <michael.williams@funsational.com>
* @author Tobias Schultze <http://tobion.de>
*/
class PdoSessionHandler implements \SessionHandlerInterface
{
/**
* @var \PDO PDO instance
*/
private $pdo;
/**
* @var string Table name
*/
private $table;
/**
* @var string Column for session id
*/
private $idCol;
/**
* @var string Column for session data
*/
private $dataCol;
/**
* @var string Column for timestamp
*/
private $timeCol;
/**
* Constructor.
*
* List of available options:
* * db_table: The name of the table [required]
* * db_id_col: The column where to store the session id [default: sess_id]
* * db_data_col: The column where to store the session data [default: sess_data]
* * db_time_col: The column where to store the timestamp [default: sess_time]
*
* @param \PDO $pdo A \PDO instance
* @param array $dbOptions An associative array of DB options
*
* @throws \InvalidArgumentException When "db_table" option is not provided
*/
public function __construct(\PDO $pdo, array $dbOptions = array())
{
if (!array_key_exists('db_table', $dbOptions)) {
throw new \InvalidArgumentException('You must provide the "db_table" option for a PdoSessionStorage.');
}
if (\PDO::ERRMODE_EXCEPTION !== $pdo->getAttribute(\PDO::ATTR_ERRMODE)) {
throw new \InvalidArgumentException(sprintf('"%s" requires PDO error mode attribute be set to throw Exceptions (i.e. $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION))', __CLASS__));
}
$this->pdo = $pdo;
$dbOptions = array_merge(array(
'db_id_col' => 'sess_id',
'db_data_col' => 'sess_data',
'db_time_col' => 'sess_time',
), $dbOptions);
$this->table = $dbOptions['db_table'];
$this->idCol = $dbOptions['db_id_col'];
$this->dataCol = $dbOptions['db_data_col'];
$this->timeCol = $dbOptions['db_time_col'];
}
/**
* {@inheritdoc}
*/
public function open($savePath, $sessionName)
{
return true;
}
/**
* {@inheritdoc}
*/
public function close()
{
return true;
}
/**
* {@inheritdoc}
*/
public function destroy($sessionId)
{
// delete the record associated with this id
$sql = "DELETE FROM $this->table WHERE $this->idCol = :id";
try {
$stmt = $this->pdo->prepare($sql);
$stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$stmt->execute();
} catch (\PDOException $e) {
throw new \RuntimeException(sprintf('PDOException was thrown when trying to delete a session: %s', $e->getMessage()), 0, $e);
}
return true;
}
/**
* {@inheritdoc}
*/
public function gc($maxlifetime)
{
// delete the session records that have expired
$sql = "DELETE FROM $this->table WHERE $this->timeCol < :time";
try {
$stmt = $this->pdo->prepare($sql);
$stmt->bindValue(':time', time() - $maxlifetime, \PDO::PARAM_INT);
$stmt->execute();
} catch (\PDOException $e) {
throw new \RuntimeException(sprintf('PDOException was thrown when trying to delete expired sessions: %s', $e->getMessage()), 0, $e);
}
return true;
}
/**
* {@inheritdoc}
*/
public function read($sessionId)
{
$sql = "SELECT $this->dataCol FROM $this->table WHERE $this->idCol = :id";
try {
$stmt = $this->pdo->prepare($sql);
$stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$stmt->execute();
// We use fetchAll instead of fetchColumn to make sure the DB cursor gets closed
$sessionRows = $stmt->fetchAll(\PDO::FETCH_NUM);
if ($sessionRows) {
return base64_decode($sessionRows[0][0]);
}
return '';
} catch (\PDOException $e) {
throw new \RuntimeException(sprintf('PDOException was thrown when trying to read the session data: %s', $e->getMessage()), 0, $e);
}
}
/**
* {@inheritdoc}
*/
public function write($sessionId, $data)
{
$encoded = base64_encode($data);
try {
// We use a single MERGE SQL query when supported by the database.
$mergeSql = $this->getMergeSql();
if (null !== $mergeSql) {
$mergeStmt = $this->pdo->prepare($mergeSql);
$mergeStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$mergeStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
$mergeStmt->bindValue(':time', time(), \PDO::PARAM_INT);
$mergeStmt->execute();
return true;
}
$updateStmt = $this->pdo->prepare(
"UPDATE $this->table SET $this->dataCol = :data, $this->timeCol = :time WHERE $this->idCol = :id"
);
$updateStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$updateStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
$updateStmt->bindValue(':time', time(), \PDO::PARAM_INT);
$updateStmt->execute();
// When MERGE is not supported, like in Postgres, we have to use this approach that can result in
// duplicate key errors when the same session is written simultaneously. We can just catch such an
// error and re-execute the update. This is similar to a serializable transaction with retry logic
// on serialization failures but without the overhead and without possible false positives due to
// longer gap locking.
if (!$updateStmt->rowCount()) {
try {
$insertStmt = $this->pdo->prepare(
"INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time)"
);
$insertStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$insertStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
$insertStmt->bindValue(':time', time(), \PDO::PARAM_INT);
$insertStmt->execute();
} catch (\PDOException $e) {
// Handle integrity violation SQLSTATE 23000 (or a subclass like 23505 in Postgres) for duplicate keys
if (0 === strpos($e->getCode(), '23')) {
$updateStmt->execute();
} else {
throw $e;
}
}
}
} catch (\PDOException $e) {
throw new \RuntimeException(sprintf('PDOException was thrown when trying to write the session data: %s', $e->getMessage()), 0, $e);
}
return true;
}
/**
* Returns a merge/upsert (i.e. insert or update) SQL query when supported by the database.
*
* @return string|null The SQL string or null when not supported
*/
private function getMergeSql()
{
$driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
switch ($driver) {
case 'mysql':
return "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
"ON DUPLICATE KEY UPDATE $this->dataCol = VALUES($this->dataCol), $this->timeCol = VALUES($this->timeCol)";
case 'oci':
// DUAL is Oracle specific dummy table
return "MERGE INTO $this->table USING DUAL ON ($this->idCol = :id) ".
"WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
"WHEN MATCHED THEN UPDATE SET $this->dataCol = :data, $this->timeCol = :time";
case 'sqlsrv' === $driver && version_compare($this->pdo->getAttribute(\PDO::ATTR_SERVER_VERSION), '10', '>='):
// MERGE is only available since SQL Server 2008 and must be terminated by semicolon
// It also requires HOLDLOCK according to http://weblogs.sqlteam.com/dang/archive/2009/01/31/UPSERT-Race-Condition-With-MERGE.aspx
return "MERGE INTO $this->table WITH (HOLDLOCK) USING (SELECT 1 AS dummy) AS src ON ($this->idCol = :id) ".
"WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
"WHEN MATCHED THEN UPDATE SET $this->dataCol = :data, $this->timeCol = :time;";
case 'sqlite':
return "INSERT OR REPLACE INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time)";
}
}
/**
* Return a PDO instance
*
* @return \PDO
*/
protected function getConnection()
{
return $this->pdo;
}
}