<?php
/*
* This file is part of the Symfony package.
*
* (c) Fabien Potencier <[email protected]>
*
* 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.
*
* It works with MySQL, PostgreSQL, Oracle, SQL Server and SQLite and implements
* different locking strategies to handle concurrent access to the same session.
* Locking is necessary to prevent loss of data due to race conditions and to keep
* the session data consistent between read() and write(). With locking, requests
* for the same session will wait until the other one finished writing. For this
* reason it's best practice to close a session as early as possible to improve
* concurrency. PHPs internal files session handler also implements locking.
*
* Attention: Since SQLite does not support row level locks but locks the whole database,
* it means only one session can be accessed at a time. Even different sessions would wait
* for another to finish. So saving session in SQLite should only be considered for
* development or prototypes.
*
* Session data is a binary string that can contain non-printable characters like the null byte.
* For this reason it must be saved in a binary column in the database like BLOB in MySQL.
* Saving it in a character column could corrupt the data. You can use createTable()
* to initialize a correctly defined table.
*
* @see https://php.net/sessionhandlerinterface
*
* @author Fabien Potencier <[email protected]>
* @author Michael Williams <[email protected]>
* @author Tobias Schultze <http://tobion.de>
*/
class PdoSessionHandler extends AbstractSessionHandler
{
/**
* No locking is done. This means sessions are prone to loss of data due to
* race conditions of concurrent requests to the same session. The last session
* write will win in this case. It might be useful when you implement your own
* logic to deal with this like an optimistic approach.
*/
public const LOCK_NONE = 0;
/**
* Creates an application-level lock on a session. The disadvantage is that the
* lock is not enforced by the database and thus other, unaware parts of the
* application could still concurrently modify the session. The advantage is it
* does not require a transaction.
* This mode is not available for SQLite and not yet implemented for oci and sqlsrv.
*/
public const LOCK_ADVISORY = 1;
/**
* Issues a real row lock. Since it uses a transaction between opening and
* closing a session, you have to be careful when you use same database connection
* that you also use for your application logic. This mode is the default because
* it's the only reliable solution across DBMSs.
*/
public const LOCK_TRANSACTIONAL = 2;
private $pdo;
/**
* DSN string or null for session.save_path or false when lazy connection disabled.
*/
private string|false|null $dsn = false;
private string $driver;
private string $table = 'sessions';
private string $idCol = 'sess_id';
private string $dataCol = 'sess_data';
private string $lifetimeCol = 'sess_lifetime';
private string $timeCol = 'sess_time';
/**
* Username when lazy-connect.
*/
private string $username = '';
/**
* Password when lazy-connect.
*/
private string $password = '';
/**
* Connection options when lazy-connect.
*/
private array $connectionOptions = [];
/**
* The strategy for locking, see constants.
*/
private int $lockMode = self::LOCK_TRANSACTIONAL;
/**
* It's an array to support multiple reads before closing which is manual, non-standard usage.
*
* @var \PDOStatement[] An array of statements to release advisory locks
*/
private array $unlockStatements = [];
/**
* True when the current session exists but expired according to session.gc_maxlifetime.
*/
private bool $sessionExpired = false;
/**
* Whether a transaction is active.
*/
private bool $inTransaction = false;
/**
* Whether gc() has been called.
*/
private bool $gcCalled = false;
/**
* You can either pass an existing database connection as PDO instance or
* pass a DSN string that will be used to lazy-connect to the database
* when the session is actually used. Furthermore it's possible to pass null
* which will then use the session.save_path ini setting as PDO DSN parameter.
*
* List of available options:
* * db_table: The name of the table [default: sessions]
* * 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_lifetime_col: The column where to store the lifetime [default: sess_lifetime]
* * db_time_col: The column where to store the timestamp [default: sess_time]
* * db_username: The username when lazy-connect [default: '']
* * db_password: The password when lazy-connect [default: '']
* * db_connection_options: An array of driver-specific connection options [default: []]
* * lock_mode: The strategy for locking, see constants [default: LOCK_TRANSACTIONAL]
*
* @param \PDO|string|null $pdoOrDsn A \PDO instance or DSN string or URL string or null
*
* @throws \InvalidArgumentException When PDO error mode is not PDO::ERRMODE_EXCEPTION
*/
public function __construct(\PDO|string $pdoOrDsn = null, array $options = [])
{
if ($pdoOrDsn instanceof \PDO) {
if (\PDO::ERRMODE_EXCEPTION !== $pdoOrDsn->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 = $pdoOrDsn;
$this->driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
} elseif (\is_string($pdoOrDsn) && str_contains($pdoOrDsn, '://')) {
$this->dsn = $this->buildDsnFromUrl($pdoOrDsn);
} else {
$this->dsn = $pdoOrDsn;
}
$this->table = $options['db_table'] ?? $this->table;
$this->idCol = $options['db_id_col'] ?? $this->idCol;
$this->dataCol = $options['db_data_col'] ?? $this->dataCol;
$this->lifetimeCol = $options['db_lifetime_col'] ?? $this->lifetimeCol;
$this->timeCol = $options['db_time_col'] ?? $this->timeCol;
$this->username = $options['db_username'] ?? $this->username;
$this->password = $options['db_password'] ?? $this->password;
$this->connectionOptions = $options['db_connection_options'] ?? $this->connectionOptions;
$this->lockMode = $options['lock_mode'] ?? $this->lockMode;
}
/**
* Creates the table to store sessions which can be called once for setup.
*
* Session ID is saved in a column of maximum length 128 because that is enough even
* for a 512 bit configured session.hash_function like Whirlpool. Session data is
* saved in a BLOB. One could also use a shorter inlined varbinary column
* if one was sure the data fits into it.
*
* @throws \PDOException When the table already exists
* @throws \DomainException When an unsupported PDO driver is used
*/
public function createTable()
{
// connect if we are not yet
$this->getConnection();
switch ($this->driver) {
case 'mysql':
// We use varbinary for the ID column because it prevents unwanted conversions:
// - character set conversions between server and client
// - trailing space removal
// - case-insensitivity
// - language processing like é == e
$sql = "CREATE TABLE $this->table ($this->idCol VARBINARY(128) NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER UNSIGNED NOT NULL, $this->timeCol INTEGER UNSIGNED NOT NULL) COLLATE utf8mb4_bin, ENGINE = InnoDB";
break;
case 'sqlite':
$sql = "CREATE TABLE $this->table ($this->idCol TEXT NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
break;
case 'pgsql':
$sql = "CREATE TABLE $this->table ($this->idCol VARCHAR(128) NOT NULL PRIMARY KEY, $this->dataCol BYTEA NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
break;
case 'oci':
$sql = "CREATE TABLE $this->table ($this->idCol VARCHAR2(128) NOT NULL PRIMARY KEY, $this->dataCol BLOB NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
break;
case 'sqlsrv':
$sql = "CREATE TABLE $this->table ($this->idCol VARCHAR(128) NOT NULL PRIMARY KEY, $this->dataCol VARBINARY(MAX) NOT NULL, $this->lifetimeCol INTEGER NOT NULL, $this->timeCol INTEGER NOT NULL)";
break;
default:
throw new \DomainException(sprintf('Creating the session table is currently not implemented for PDO driver "%s".', $this->driver));
}
try {
$this->pdo->exec($sql);
$this->pdo->exec("CREATE INDEX EXPIRY ON $this->table ($this->lifetimeCol)");
} catch (\PDOException $e) {
$this->rollback();
throw $e;
}
}
/**
* Returns true when the current session exists but expired according to session.gc_maxlifetime.
*
* Can be used to distinguish between a new session and one that expired due to inactivity.
*/
public function isSessionExpired(): bool
{
return $this->sessionExpired;
}
public function open(string $savePath, string $sessionName): bool
{
$this->sessionExpired = false;
if (!isset($this->pdo)) {
$this->connect($this->dsn ?: $savePath);
}
return parent::open($savePath, $sessionName);
}
public function read(string $sessionId): string
{
try {
return parent::read($sessionId);
} catch (\PDOException $e) {
$this->rollback();
throw $e;
}
}
public function gc(int $maxlifetime): int|false
{
// We delay gc() to close() so that it is executed outside the transactional and blocking read-write process.
// This way, pruning expired sessions does not block them from being started while the current session is used.
$this->gcCalled = true;
return 0;
}
/**
* {@inheritdoc}
*/
protected function doDestroy(string $sessionId): bool
{
// 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) {
$this->rollback();
throw $e;
}
return true;
}
/**
* {@inheritdoc}
*/
protected function doWrite(string $sessionId, string $data): bool
{
$maxlifetime = (int) \ini_get('session.gc_maxlifetime');
try {
// We use a single MERGE SQL query when supported by the database.
$mergeStmt = $this->getMergeStatement($sessionId, $data, $maxlifetime);
if (null !== $mergeStmt) {
$mergeStmt->execute();
return true;
}
$updateStmt = $this->getUpdateStatement($sessionId, $data, $maxlifetime);
$updateStmt->execute();
// When MERGE is not supported, like in Postgres < 9.5, we have to use this approach that can result in
// duplicate key errors when the same session is written simultaneously (given the LOCK_NONE behavior).
// We can just catch such an error and re-execute the update. This is similar to a serializable
// transaction with retry logic on serialization failures but without the overhead and without possible
// false positives due to longer gap locking.
if (!$updateStmt->rowCount()) {
try {
$insertStmt = $this->getInsertStatement($sessionId, $data, $maxlifetime);
$insertStmt->execute();
} catch (\PDOException $e) {
// Handle integrity violation SQLSTATE 23000 (or a subclass like 23505 in Postgres) for duplicate keys
if (str_starts_with($e->getCode(), '23')) {
$updateStmt->execute();
} else {
throw $e;
}
}
}
} catch (\PDOException $e) {
$this->rollback();
throw $e;
}
return true;
}
public function updateTimestamp(string $sessionId, string $data): bool
{
$expiry = time() + (int) \ini_get('session.gc_maxlifetime');
try {
$updateStmt = $this->pdo->prepare(
"UPDATE $this->table SET $this->lifetimeCol = :expiry, $this->timeCol = :time WHERE $this->idCol = :id"
);
$updateStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$updateStmt->bindParam(':expiry', $expiry, \PDO::PARAM_INT);
$updateStmt->bindValue(':time', time(), \PDO::PARAM_INT);
$updateStmt->execute();
} catch (\PDOException $e) {
$this->rollback();
throw $e;
}
return true;
}
public function close(): bool
{
$this->commit();
while ($unlockStmt = array_shift($this->unlockStatements)) {
$unlockStmt->execute();
}
if ($this->gcCalled) {
$this->gcCalled = false;
// delete the session records that have expired
$sql = "DELETE FROM $this->table WHERE $this->lifetimeCol < :time";
$stmt = $this->pdo->prepare($sql);
$stmt->bindValue(':time', time(), \PDO::PARAM_INT);
$stmt->execute();
}
if (false !== $this->dsn) {
unset($this->pdo, $this->driver); // only close lazy-connection
}
return true;
}
/**
* Lazy-connects to the database.
*/
private function connect(string $dsn): void
{
$this->pdo = new \PDO($dsn, $this->username, $this->password, $this->connectionOptions);
$this->pdo->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
$this->driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
}
/**
* Builds a PDO DSN from a URL-like connection string.
*
* @todo implement missing support for oci DSN (which look totally different from other PDO ones)
*/
private function buildDsnFromUrl(string $dsnOrUrl): string
{
// (pdo_)?sqlite3?:///... => (pdo_)?sqlite3?://localhost/... or else the URL will be invalid
$url = preg_replace('#^((?:pdo_)?sqlite3?):///#', '$1://localhost/', $dsnOrUrl);
$params = parse_url($url);
if (false === $params) {
return $dsnOrUrl; // If the URL is not valid, let's assume it might be a DSN already.
}
$params = array_map('rawurldecode', $params);
// Override the default username and password. Values passed through options will still win over these in the constructor.
if (isset($params['user'])) {
$this->username = $params['user'];
}
if (isset($params['pass'])) {
$this->password = $params['pass'];
}
if (!isset($params['scheme'])) {
throw new \InvalidArgumentException('URLs without scheme are not supported to configure the PdoSessionHandler.');
}
$driverAliasMap = [
'mssql' => 'sqlsrv',
'mysql2' => 'mysql', // Amazon RDS, for some weird reason
'postgres' => 'pgsql',
'postgresql' => 'pgsql',
'sqlite3' => 'sqlite',
];
$driver = $driverAliasMap[$params['scheme']] ?? $params['scheme'];
// Doctrine DBAL supports passing its internal pdo_* driver names directly too (allowing both dashes and underscores). This allows supporting the same here.
if (str_starts_with($driver, 'pdo_') || str_starts_with($driver, 'pdo-')) {
$driver = substr($driver, 4);
}
$dsn = null;
switch ($driver) {
case 'mysql':
$dsn = 'mysql:';
if ('' !== ($params['query'] ?? '')) {
$queryParams = [];
parse_str($params['query'], $queryParams);
if ('' !== ($queryParams['charset'] ?? '')) {
$dsn .= 'charset='.$queryParams['charset'].';';
}
if ('' !== ($queryParams['unix_socket'] ?? '')) {
$dsn .= 'unix_socket='.$queryParams['unix_socket'].';';
if (isset($params['path'])) {
$dbName = substr($params['path'], 1); // Remove the leading slash
$dsn .= 'dbname='.$dbName.';';
}
return $dsn;
}
}
// If "unix_socket" is not in the query, we continue with the same process as pgsql
// no break
case 'pgsql':
$dsn ?? $dsn = 'pgsql:';
if (isset($params['host']) && '' !== $params['host']) {
$dsn .= 'host='.$params['host'].';';
}
if (isset($params['port']) && '' !== $params['port']) {
$dsn .= 'port='.$params['port'].';';
}
if (isset($params['path'])) {
$dbName = substr($params['path'], 1); // Remove the leading slash
$dsn .= 'dbname='.$dbName.';';
}
return $dsn;
case 'sqlite':
return 'sqlite:'.substr($params['path'], 1);
case 'sqlsrv':
$dsn = 'sqlsrv:server=';
if (isset($params['host'])) {
$dsn .= $params['host'];
}
if (isset($params['port']) && '' !== $params['port']) {
$dsn .= ','.$params['port'];
}
if (isset($params['path'])) {
$dbName = substr($params['path'], 1); // Remove the leading slash
$dsn .= ';Database='.$dbName;
}
return $dsn;
default:
throw new \InvalidArgumentException(sprintf('The scheme "%s" is not supported by the PdoSessionHandler URL configuration. Pass a PDO DSN directly.', $params['scheme']));
}
}
/**
* Helper method to begin a transaction.
*
* Since SQLite does not support row level locks, we have to acquire a reserved lock
* on the database immediately. Because of https://bugs.php.net/42766 we have to create
* such a transaction manually which also means we cannot use PDO::commit or
* PDO::rollback or PDO::inTransaction for SQLite.
*
* Also MySQLs default isolation, REPEATABLE READ, causes deadlock for different sessions
* due to https://percona.com/blog/2013/12/12/one-more-innodb-gap-lock-to-avoid/ .
* So we change it to READ COMMITTED.
*/
private function beginTransaction(): void
{
if (!$this->inTransaction) {
if ('sqlite' === $this->driver) {
$this->pdo->exec('BEGIN IMMEDIATE TRANSACTION');
} else {
if ('mysql' === $this->driver) {
$this->pdo->exec('SET TRANSACTION ISOLATION LEVEL READ COMMITTED');
}
$this->pdo->beginTransaction();
}
$this->inTransaction = true;
}
}
/**
* Helper method to commit a transaction.
*/
private function commit(): void
{
if ($this->inTransaction) {
try {
// commit read-write transaction which also releases the lock
if ('sqlite' === $this->driver) {
$this->pdo->exec('COMMIT');
} else {
$this->pdo->commit();
}
$this->inTransaction = false;
} catch (\PDOException $e) {
$this->rollback();
throw $e;
}
}
}
/**
* Helper method to rollback a transaction.
*/
private function rollback(): void
{
// We only need to rollback if we are in a transaction. Otherwise the resulting
// error would hide the real problem why rollback was called. We might not be
// in a transaction when not using the transactional locking behavior or when
// two callbacks (e.g. destroy and write) are invoked that both fail.
if ($this->inTransaction) {
if ('sqlite' === $this->driver) {
$this->pdo->exec('ROLLBACK');
} else {
$this->pdo->rollBack();
}
$this->inTransaction = false;
}
}
/**
* Reads the session data in respect to the different locking strategies.
*
* We need to make sure we do not return session data that is already considered garbage according
* to the session.gc_maxlifetime setting because gc() is called after read() and only sometimes.
*/
protected function doRead(string $sessionId): string
{
if (self::LOCK_ADVISORY === $this->lockMode) {
$this->unlockStatements[] = $this->doAdvisoryLock($sessionId);
}
$selectSql = $this->getSelectSql();
$selectStmt = $this->pdo->prepare($selectSql);
$selectStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$insertStmt = null;
while (true) {
$selectStmt->execute();
$sessionRows = $selectStmt->fetchAll(\PDO::FETCH_NUM);
if ($sessionRows) {
$expiry = (int) $sessionRows[0][1];
if ($expiry < time()) {
$this->sessionExpired = true;
return '';
}
return \is_resource($sessionRows[0][0]) ? stream_get_contents($sessionRows[0][0]) : $sessionRows[0][0];
}
if (null !== $insertStmt) {
$this->rollback();
throw new \RuntimeException('Failed to read session: INSERT reported a duplicate id but next SELECT did not return any data.');
}
if (!filter_var(\ini_get('session.use_strict_mode'), \FILTER_VALIDATE_BOOLEAN) && self::LOCK_TRANSACTIONAL === $this->lockMode && 'sqlite' !== $this->driver) {
// In strict mode, session fixation is not possible: new sessions always start with a unique
// random id, so that concurrency is not possible and this code path can be skipped.
// Exclusive-reading of non-existent rows does not block, so we need to do an insert to block
// until other connections to the session are committed.
try {
$insertStmt = $this->getInsertStatement($sessionId, '', 0);
$insertStmt->execute();
} catch (\PDOException $e) {
// Catch duplicate key error because other connection created the session already.
// It would only not be the case when the other connection destroyed the session.
if (str_starts_with($e->getCode(), '23')) {
// Retrieve finished session data written by concurrent connection by restarting the loop.
// We have to start a new transaction as a failed query will mark the current transaction as
// aborted in PostgreSQL and disallow further queries within it.
$this->rollback();
$this->beginTransaction();
continue;
}
throw $e;
}
}
return '';
}
}
/**
* Executes an application-level lock on the database.
*
* @return \PDOStatement The statement that needs to be executed later to release the lock
*
* @throws \DomainException When an unsupported PDO driver is used
*
* @todo implement missing advisory locks
* - for oci using DBMS_LOCK.REQUEST
* - for sqlsrv using sp_getapplock with LockOwner = Session
*/
private function doAdvisoryLock(string $sessionId): \PDOStatement
{
switch ($this->driver) {
case 'mysql':
// MySQL 5.7.5 and later enforces a maximum length on lock names of 64 characters. Previously, no limit was enforced.
$lockId = substr($sessionId, 0, 64);
// should we handle the return value? 0 on timeout, null on error
// we use a timeout of 50 seconds which is also the default for innodb_lock_wait_timeout
$stmt = $this->pdo->prepare('SELECT GET_LOCK(:key, 50)');
$stmt->bindValue(':key', $lockId, \PDO::PARAM_STR);
$stmt->execute();
$releaseStmt = $this->pdo->prepare('DO RELEASE_LOCK(:key)');
$releaseStmt->bindValue(':key', $lockId, \PDO::PARAM_STR);
return $releaseStmt;
case 'pgsql':
// Obtaining an exclusive session level advisory lock requires an integer key.
// When session.sid_bits_per_character > 4, the session id can contain non-hex-characters.
// So we cannot just use hexdec().
if (4 === \PHP_INT_SIZE) {
$sessionInt1 = $this->convertStringToInt($sessionId);
$sessionInt2 = $this->convertStringToInt(substr($sessionId, 4, 4));
$stmt = $this->pdo->prepare('SELECT pg_advisory_lock(:key1, :key2)');
$stmt->bindValue(':key1', $sessionInt1, \PDO::PARAM_INT);
$stmt->bindValue(':key2', $sessionInt2, \PDO::PARAM_INT);
$stmt->execute();
$releaseStmt = $this->pdo->prepare('SELECT pg_advisory_unlock(:key1, :key2)');
$releaseStmt->bindValue(':key1', $sessionInt1, \PDO::PARAM_INT);
$releaseStmt->bindValue(':key2', $sessionInt2, \PDO::PARAM_INT);
} else {
$sessionBigInt = $this->convertStringToInt($sessionId);
$stmt = $this->pdo->prepare('SELECT pg_advisory_lock(:key)');
$stmt->bindValue(':key', $sessionBigInt, \PDO::PARAM_INT);
$stmt->execute();
$releaseStmt = $this->pdo->prepare('SELECT pg_advisory_unlock(:key)');
$releaseStmt->bindValue(':key', $sessionBigInt, \PDO::PARAM_INT);
}
return $releaseStmt;
case 'sqlite':
throw new \DomainException('SQLite does not support advisory locks.');
default:
throw new \DomainException(sprintf('Advisory locks are currently not implemented for PDO driver "%s".', $this->driver));
}
}
/**
* Encodes the first 4 (when PHP_INT_SIZE == 4) or 8 characters of the string as an integer.
*
* Keep in mind, PHP integers are signed.
*/
private function convertStringToInt(string $string): int
{
if (4 === \PHP_INT_SIZE) {
return (\ord($string[3]) << 24) + (\ord($string[2]) << 16) + (\ord($string[1]) << 8) + \ord($string[0]);
}
$int1 = (\ord($string[7]) << 24) + (\ord($string[6]) << 16) + (\ord($string[5]) << 8) + \ord($string[4]);
$int2 = (\ord($string[3]) << 24) + (\ord($string[2]) << 16) + (\ord($string[1]) << 8) + \ord($string[0]);
return $int2 + ($int1 << 32);
}
/**
* Return a locking or nonlocking SQL query to read session information.
*
* @throws \DomainException When an unsupported PDO driver is used
*/
private function getSelectSql(): string
{
if (self::LOCK_TRANSACTIONAL === $this->lockMode) {
$this->beginTransaction();
switch ($this->driver) {
case 'mysql':
case 'oci':
case 'pgsql':
return "SELECT $this->dataCol, $this->lifetimeCol FROM $this->table WHERE $this->idCol = :id FOR UPDATE";
case 'sqlsrv':
return "SELECT $this->dataCol, $this->lifetimeCol FROM $this->table WITH (UPDLOCK, ROWLOCK) WHERE $this->idCol = :id";
case 'sqlite':
// we already locked when starting transaction
break;
default:
throw new \DomainException(sprintf('Transactional locks are currently not implemented for PDO driver "%s".', $this->driver));
}
}
return "SELECT $this->dataCol, $this->lifetimeCol FROM $this->table WHERE $this->idCol = :id";
}
/**
* Returns an insert statement supported by the database for writing session data.
*/
private function getInsertStatement(string $sessionId, string $sessionData, int $maxlifetime): \PDOStatement
{
switch ($this->driver) {
case 'oci':
$data = fopen('php://memory', 'r+');
fwrite($data, $sessionData);
rewind($data);
$sql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, EMPTY_BLOB(), :expiry, :time) RETURNING $this->dataCol into :data";
break;
default:
$data = $sessionData;
$sql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :expiry, :time)";
break;
}
$stmt = $this->pdo->prepare($sql);
$stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$stmt->bindParam(':data', $data, \PDO::PARAM_LOB);
$stmt->bindValue(':expiry', time() + $maxlifetime, \PDO::PARAM_INT);
$stmt->bindValue(':time', time(), \PDO::PARAM_INT);
return $stmt;
}
/**
* Returns an update statement supported by the database for writing session data.
*/
private function getUpdateStatement(string $sessionId, string $sessionData, int $maxlifetime): \PDOStatement
{
switch ($this->driver) {
case 'oci':
$data = fopen('php://memory', 'r+');
fwrite($data, $sessionData);
rewind($data);
$sql = "UPDATE $this->table SET $this->dataCol = EMPTY_BLOB(), $this->lifetimeCol = :expiry, $this->timeCol = :time WHERE $this->idCol = :id RETURNING $this->dataCol into :data";
break;
default:
$data = $sessionData;
$sql = "UPDATE $this->table SET $this->dataCol = :data, $this->lifetimeCol = :expiry, $this->timeCol = :time WHERE $this->idCol = :id";
break;
}
$stmt = $this->pdo->prepare($sql);
$stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$stmt->bindParam(':data', $data, \PDO::PARAM_LOB);
$stmt->bindValue(':expiry', time() + $maxlifetime, \PDO::PARAM_INT);
$stmt->bindValue(':time', time(), \PDO::PARAM_INT);
return $stmt;
}
/**
* Returns a merge/upsert (i.e. insert or update) statement when supported by the database for writing session data.
*/
private function getMergeStatement(string $sessionId, string $data, int $maxlifetime): ?\PDOStatement
{
switch (true) {
case 'mysql' === $this->driver:
$mergeSql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :expiry, :time) ".
"ON DUPLICATE KEY UPDATE $this->dataCol = VALUES($this->dataCol), $this->lifetimeCol = VALUES($this->lifetimeCol), $this->timeCol = VALUES($this->timeCol)";
break;
case 'sqlsrv' === $this->driver && version_compare($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 https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/
$mergeSql = "MERGE INTO $this->table WITH (HOLDLOCK) USING (SELECT 1 AS dummy) AS src ON ($this->idCol = ?) ".
"WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (?, ?, ?, ?) ".
"WHEN MATCHED THEN UPDATE SET $this->dataCol = ?, $this->lifetimeCol = ?, $this->timeCol = ?;";
break;
case 'sqlite' === $this->driver:
$mergeSql = "INSERT OR REPLACE INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :expiry, :time)";
break;
case 'pgsql' === $this->driver && version_compare($this->pdo->getAttribute(\PDO::ATTR_SERVER_VERSION), '9.5', '>='):
$mergeSql = "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->lifetimeCol, $this->timeCol) VALUES (:id, :data, :expiry, :time) ".
"ON CONFLICT ($this->idCol) DO UPDATE SET ($this->dataCol, $this->lifetimeCol, $this->timeCol) = (EXCLUDED.$this->dataCol, EXCLUDED.$this->lifetimeCol, EXCLUDED.$this->timeCol)";
break;
default:
// MERGE is not supported with LOBs: https://oracle.com/technetwork/articles/fuecks-lobs-095315.html
return null;
}
$mergeStmt = $this->pdo->prepare($mergeSql);
if ('sqlsrv' === $this->driver) {
$mergeStmt->bindParam(1, $sessionId, \PDO::PARAM_STR);
$mergeStmt->bindParam(2, $sessionId, \PDO::PARAM_STR);
$mergeStmt->bindParam(3, $data, \PDO::PARAM_LOB);
$mergeStmt->bindValue(4, time() + $maxlifetime, \PDO::PARAM_INT);
$mergeStmt->bindValue(5, time(), \PDO::PARAM_INT);
$mergeStmt->bindParam(6, $data, \PDO::PARAM_LOB);
$mergeStmt->bindValue(7, time() + $maxlifetime, \PDO::PARAM_INT);
$mergeStmt->bindValue(8, time(), \PDO::PARAM_INT);
} else {
$mergeStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
$mergeStmt->bindParam(':data', $data, \PDO::PARAM_LOB);
$mergeStmt->bindValue(':expiry', time() + $maxlifetime, \PDO::PARAM_INT);
$mergeStmt->bindValue(':time', time(), \PDO::PARAM_INT);
}
return $mergeStmt;
}
/**
* Return a PDO instance.
*/
protected function getConnection(): \PDO
{
if (!isset($this->pdo)) {
$this->connect($this->dsn ?: \ini_get('session.save_path'));
}
return $this->pdo;
}
}