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PdoSessionHandler.php
001 <?php
002
003 /*
004 * This file is part of the Symfony package.
005 *
006 * (c) Fabien Potencier <fabien@symfony.com>
007 *
008 * For the full copyright and license information, please view the LICENSE
009 * file that was distributed with this source code.
010 */
011
012 namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;
013
014 /**
015 * Session handler using a PDO connection to read and write data.
016 *
017 * Session data is a binary string that can contain non-printable characters like the null byte.
018 * For this reason this handler base64 encodes the data to be able to save it in a character column.
019 *
020 * This version of the PdoSessionHandler does NOT implement locking. So concurrent requests to the
021 * same session can result in data loss due to race conditions.
022 *
023 * @author Fabien Potencier <fabien@symfony.com>
024 * @author Michael Williams <michael.williams@funsational.com>
025 * @author Tobias Schultze <http://tobion.de>
026 */
027 class PdoSessionHandler implements \SessionHandlerInterface
028 {
029 /**
030 * @var \PDO PDO instance
031 */
032 private $pdo;
033
034 /**
035 * @var string Table name
036 */
037 private $table;
038
039 /**
040 * @var string Column for session id
041 */
042 private $idCol;
043
044 /**
045 * @var string Column for session data
046 */
047 private $dataCol;
048
049 /**
050 * @var string Column for timestamp
051 */
052 private $timeCol;
053
054 /**
055 * Constructor.
056 *
057 * List of available options:
058 * * db_table: The name of the table [required]
059 * * db_id_col: The column where to store the session id [default: sess_id]
060 * * db_data_col: The column where to store the session data [default: sess_data]
061 * * db_time_col: The column where to store the timestamp [default: sess_time]
062 *
063 * @param \PDO $pdo A \PDO instance
064 * @param array $dbOptions An associative array of DB options
065 *
066 * @throws \InvalidArgumentException When "db_table" option is not provided
067 */
068 public function __construct(\PDO $pdo, array $dbOptions = array())
069 {
070 if (!array_key_exists('db_table', $dbOptions)) {
071 throw new \InvalidArgumentException('You must provide the "db_table" option for a PdoSessionStorage.');
072 }
073 if (\PDO::ERRMODE_EXCEPTION !== $pdo->getAttribute(\PDO::ATTR_ERRMODE)) {
074 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__));
075 }
076 $this->pdo = $pdo;
077 $dbOptions = array_merge(array(
078 'db_id_col' => 'sess_id',
079 'db_data_col' => 'sess_data',
080 'db_time_col' => 'sess_time',
081 ), $dbOptions);
082
083 $this->table = $dbOptions['db_table'];
084 $this->idCol = $dbOptions['db_id_col'];
085 $this->dataCol = $dbOptions['db_data_col'];
086 $this->timeCol = $dbOptions['db_time_col'];
087 }
088
089 /**
090 * {@inheritdoc}
091 */
092 public function open($savePath, $sessionName)
093 {
094 return true;
095 }
096
097 /**
098 * {@inheritdoc}
099 */
100 public function close()
101 {
102 return true;
103 }
104
105 /**
106 * {@inheritdoc}
107 */
108 public function destroy($sessionId)
109 {
110 // delete the record associated with this id
111 $sql = "DELETE FROM $this->table WHERE $this->idCol = :id";
112
113 try {
114 $stmt = $this->pdo->prepare($sql);
115 $stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
116 $stmt->execute();
117 } catch (\PDOException $e) {
118 throw new \RuntimeException(sprintf('PDOException was thrown when trying to delete a session: %s', $e->getMessage()), 0, $e);
119 }
120
121 return true;
122 }
123
124 /**
125 * {@inheritdoc}
126 */
127 public function gc($maxlifetime)
128 {
129 // delete the session records that have expired
130 $sql = "DELETE FROM $this->table WHERE $this->timeCol < :time";
131
132 try {
133 $stmt = $this->pdo->prepare($sql);
134 $stmt->bindValue(':time', time() - $maxlifetime, \PDO::PARAM_INT);
135 $stmt->execute();
136 } catch (\PDOException $e) {
137 throw new \RuntimeException(sprintf('PDOException was thrown when trying to delete expired sessions: %s', $e->getMessage()), 0, $e);
138 }
139
140 return true;
141 }
142
143 /**
144 * {@inheritdoc}
145 */
146 public function read($sessionId)
147 {
148 $sql = "SELECT $this->dataCol FROM $this->table WHERE $this->idCol = :id";
149
150 try {
151 $stmt = $this->pdo->prepare($sql);
152 $stmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
153 $stmt->execute();
154
155 // We use fetchAll instead of fetchColumn to make sure the DB cursor gets closed
156 $sessionRows = $stmt->fetchAll(\PDO::FETCH_NUM);
157
158 if ($sessionRows) {
159 return base64_decode($sessionRows[0][0]);
160 }
161
162 return '';
163 } catch (\PDOException $e) {
164 throw new \RuntimeException(sprintf('PDOException was thrown when trying to read the session data: %s', $e->getMessage()), 0, $e);
165 }
166 }
167
168 /**
169 * {@inheritdoc}
170 */
171 public function write($sessionId, $data)
172 {
173 $encoded = base64_encode($data);
174
175 try {
176 // We use a single MERGE SQL query when supported by the database.
177 $mergeSql = $this->getMergeSql();
178
179 if (null !== $mergeSql) {
180 $mergeStmt = $this->pdo->prepare($mergeSql);
181 $mergeStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
182 $mergeStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
183 $mergeStmt->bindValue(':time', time(), \PDO::PARAM_INT);
184 $mergeStmt->execute();
185
186 return true;
187 }
188
189 $updateStmt = $this->pdo->prepare(
190 "UPDATE $this->table SET $this->dataCol = :data, $this->timeCol = :time WHERE $this->idCol = :id"
191 );
192 $updateStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
193 $updateStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
194 $updateStmt->bindValue(':time', time(), \PDO::PARAM_INT);
195 $updateStmt->execute();
196
197 // When MERGE is not supported, like in Postgres, we have to use this approach that can result in
198 // duplicate key errors when the same session is written simultaneously. We can just catch such an
199 // error and re-execute the update. This is similar to a serializable transaction with retry logic
200 // on serialization failures but without the overhead and without possible false positives due to
201 // longer gap locking.
202 if (!$updateStmt->rowCount()) {
203 try {
204 $insertStmt = $this->pdo->prepare(
205 "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time)"
206 );
207 $insertStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
208 $insertStmt->bindParam(':data', $encoded, \PDO::PARAM_STR);
209 $insertStmt->bindValue(':time', time(), \PDO::PARAM_INT);
210 $insertStmt->execute();
211 } catch (\PDOException $e) {
212 // Handle integrity violation SQLSTATE 23000 (or a subclass like 23505 in Postgres) for duplicate keys
213 if (0 === strpos($e->getCode(), '23')) {
214 $updateStmt->execute();
215 } else {
216 throw $e;
217 }
218 }
219 }
220 } catch (\PDOException $e) {
221 throw new \RuntimeException(sprintf('PDOException was thrown when trying to write the session data: %s', $e->getMessage()), 0, $e);
222 }
223
224 return true;
225 }
226
227 /**
228 * Returns a merge/upsert (i.e. insert or update) SQL query when supported by the database.
229 *
230 * @return string|null The SQL string or null when not supported
231 */
232 private function getMergeSql()
233 {
234 $driver = $this->pdo->getAttribute(\PDO::ATTR_DRIVER_NAME);
235
236 switch ($driver) {
237 case 'mysql':
238 return "INSERT INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
239 "ON DUPLICATE KEY UPDATE $this->dataCol = VALUES($this->dataCol), $this->timeCol = VALUES($this->timeCol)";
240 case 'oci':
241 // DUAL is Oracle specific dummy table
242 return "MERGE INTO $this->table USING DUAL ON ($this->idCol = :id) ".
243 "WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
244 "WHEN MATCHED THEN UPDATE SET $this->dataCol = :data, $this->timeCol = :time";
245 case 'sqlsrv' === $driver && version_compare($this->pdo->getAttribute(\PDO::ATTR_SERVER_VERSION), '10', '>='):
246 // MERGE is only available since SQL Server 2008 and must be terminated by semicolon
247 // It also requires HOLDLOCK according to http://weblogs.sqlteam.com/dang/archive/2009/01/31/UPSERT-Race-Condition-With-MERGE.aspx
248 return "MERGE INTO $this->table WITH (HOLDLOCK) USING (SELECT 1 AS dummy) AS src ON ($this->idCol = :id) ".
249 "WHEN NOT MATCHED THEN INSERT ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time) ".
250 "WHEN MATCHED THEN UPDATE SET $this->dataCol = :data, $this->timeCol = :time;";
251 case 'sqlite':
252 return "INSERT OR REPLACE INTO $this->table ($this->idCol, $this->dataCol, $this->timeCol) VALUES (:id, :data, :time)";
253 }
254 }
255 }
256