Complex classes like Database often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use Database, and based on these observations, apply Extract Interface, too.
| 1 | <?php |
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| 247 | Class Database { |
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| 248 | |||
| 249 | /** |
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| 250 | * Constant to indicate whether the query is a write operation. |
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| 251 | * |
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| 252 | * @var integer |
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| 253 | */ |
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| 254 | const __WRITE_OPERATION__ = 0; |
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| 255 | |||
| 256 | /** |
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| 257 | * Constant to indicate whether the query is a write operation |
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| 258 | * |
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| 259 | * @var integer |
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| 260 | */ |
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| 261 | const __READ_OPERATION__ = 1; |
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| 262 | |||
| 263 | /** |
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| 264 | * An instance of the current PDO object |
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| 265 | * @var PDO |
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| 266 | */ |
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| 267 | public $conn = null; |
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| 268 | |||
| 269 | /** |
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| 270 | * Sets the current `$_log` to be an empty array |
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| 271 | * |
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| 272 | * @var array |
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| 273 | */ |
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| 274 | public $log = array(); |
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| 275 | |||
| 276 | /** |
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| 277 | * The number of queries this class has executed, defaults to 0. |
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| 278 | * |
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| 279 | * @var integer |
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| 280 | */ |
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| 281 | private $_query_count = 0; |
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| 282 | |||
| 283 | /** |
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| 284 | * The table prefix for this connection. Queries to be written using |
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| 285 | * a `tbl_table_name` syntax, where `tbl_` will be replaced by this |
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| 286 | * variable. By default it is `sym_` but it configured in the configuration |
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| 287 | * |
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| 288 | * @var string |
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| 289 | */ |
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| 290 | private $_prefix = 'sym_'; |
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| 291 | |||
| 292 | /** |
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| 293 | * Whether query caching is enabled or not. By default this set |
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| 294 | * to true which will use SQL_CACHE to cache the results of queries |
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| 295 | * |
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| 296 | * @var boolean |
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| 297 | */ |
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| 298 | private $_cache = true; |
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| 299 | |||
| 300 | /** |
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| 301 | * Whether to log this query in the internal `$log`. |
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| 302 | * Defaults to true |
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| 303 | * |
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| 304 | * @var boolean |
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| 305 | */ |
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| 306 | private $_logging = true; |
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| 307 | |||
| 308 | /** |
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| 309 | * Resets the result, `$this->_lastResult` and `$this->_lastQuery` to their empty |
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| 310 | * values. Called on each query and when the class is destroyed. |
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| 311 | */ |
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| 312 | public function flush() |
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| 319 | |||
| 320 | /** |
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| 321 | * Creates a new Database object given an associative array of configuration |
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| 322 | * parameters in `$config`. If `$config` contains a key, `pdo` then this |
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| 323 | * `Database` instance will use that PDO connection. Otherwise, `$config` |
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| 324 | * should include `driver`, `host`, `port`, `user`, `password` and an optional |
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| 325 | * array of PDO options in `options`. |
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| 326 | * |
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| 327 | * @param array $config |
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| 328 | * @return PDO |
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| 329 | */ |
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| 330 | public function __construct(array $config = array()) |
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| 347 | |||
| 348 | /** |
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| 349 | * Magic function that will flush the MySQL log and close the MySQL |
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| 350 | * connection when the MySQL class is removed or destroyed. |
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| 351 | * |
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| 352 | * @link http://php.net/manual/en/language.oop5.decon.php |
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| 353 | */ |
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| 354 | public function __destruct() |
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| 359 | |||
| 360 | /** |
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| 361 | * Creates a PDO connection to the desired database given the parameters. |
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| 362 | * This will also set the error mode to be exceptions (handled by this class) |
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| 363 | * |
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| 364 | * @link http://www.php.net/manual/en/pdo.drivers.php |
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| 365 | * @param string $dsn |
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| 366 | * @param string $username |
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| 367 | * @param string $password |
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| 368 | * @param array $options |
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| 369 | * @return boolean |
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| 370 | */ |
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| 371 | public function connect($dsn = null, $username = null, $password = null, array $options = array()) |
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| 385 | |||
| 386 | /** |
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| 387 | * Returns the number of queries that has been executed |
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| 388 | * |
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| 389 | * @return integer |
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| 390 | */ |
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| 391 | public function queryCount() |
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| 395 | |||
| 396 | /** |
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| 397 | * Sets query caching to true, this will prepend all READ_OPERATION |
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| 398 | * queries with SQL_CACHE. Symphony be default enables caching. It |
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| 399 | * can be turned off by setting the query_cache parameter to 'off' in the |
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| 400 | * Symphony config file. |
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| 401 | * |
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| 402 | * @link http://dev.mysql.com/doc/refman/5.1/en/query-cache.html |
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| 403 | */ |
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| 404 | public function enableCaching() |
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| 408 | |||
| 409 | /** |
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| 410 | * Sets query caching to false, this will prepend all READ_OPERATION |
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| 411 | * queries will SQL_NO_CACHE. |
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| 412 | */ |
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| 413 | public function disableCaching() |
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| 417 | |||
| 418 | /** |
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| 419 | * Returns boolean if query caching is enabled or not |
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| 420 | * |
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| 421 | * @return boolean |
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| 422 | */ |
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| 423 | public function isCachingEnabled() |
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| 427 | |||
| 428 | /** |
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| 429 | * Enables the logging of queries |
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| 430 | */ |
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| 431 | public function enableLogging() |
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| 435 | |||
| 436 | /** |
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| 437 | * Sets logging to false |
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| 438 | */ |
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| 439 | public function disableLogging() |
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| 443 | |||
| 444 | /** |
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| 445 | * Returns boolean if logging is enabled or not |
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| 446 | * |
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| 447 | * @return boolean |
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| 448 | */ |
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| 449 | public function isLoggingEnabled() |
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| 453 | |||
| 454 | /** |
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| 455 | * Symphony uses a prefix for all it's database tables so it can live peacefully |
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| 456 | * on the same database as other applications. By default this is sym_, but it |
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| 457 | * can be changed when Symphony is installed. |
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| 458 | * |
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| 459 | * @param string $prefix |
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| 460 | * The table prefix for Symphony, by default this is sym_ |
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| 461 | */ |
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| 462 | public function setPrefix($prefix) |
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| 466 | |||
| 467 | /** |
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| 468 | * Returns the prefix used by Symphony for this Database instance. |
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| 469 | * |
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| 470 | * @since Symphony 2.4 |
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| 471 | * @return string |
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| 472 | */ |
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| 473 | public function getPrefix() |
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| 477 | |||
| 478 | /** |
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| 479 | * Given a string, replace the default table prefixes with the |
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| 480 | * table prefix for this database instance. |
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| 481 | * |
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| 482 | * @param string $query |
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| 483 | * @return string |
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| 484 | */ |
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| 485 | public function replaceTablePrefix($query) |
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| 493 | |||
| 494 | /** |
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| 495 | * Function looks over a query to determine if it's a READ or WRITE operation. |
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| 496 | * WRITE operations are any query that starts with: SET, CREATE, INSERT, REPLACE |
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| 497 | * ALTER, DELETE, UPDATE, OPTIMIZE, TRUNCATE or DROP. All other queries are considered |
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| 498 | * READ operations |
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| 499 | * |
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| 500 | * @param string $query |
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| 501 | * @return integer |
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| 502 | */ |
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| 503 | public function determineQueryType($query) |
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| 509 | |||
| 510 | /** |
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| 511 | * @param array $values |
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| 512 | * @return string |
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| 513 | */ |
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| 514 | public static function addPlaceholders(array $values = array()) |
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| 523 | |||
| 524 | /** |
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| 525 | * Given a query that has been prepared and an array of values to subsitute |
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| 526 | * into the query, the function will return the result. |
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| 527 | * |
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| 528 | * @param string $query |
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| 529 | * @param array $values |
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| 530 | * @return PDOStatement |
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| 531 | */ |
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| 532 | public function insert($query, array $values) |
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| 538 | |||
| 539 | /** |
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| 540 | * Returns the last insert ID from the previous query. This is |
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| 541 | * the value from an auto_increment field. |
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| 542 | * |
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| 543 | * @return integer |
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| 544 | * The last interested row's ID |
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| 545 | */ |
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| 546 | public function getInsertID() |
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| 550 | |||
| 551 | /** |
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| 552 | * Given a query that has been prepared and an array of values to subsitute |
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| 553 | * into the query, the function will return the result. |
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| 554 | * |
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| 555 | * @param string $query |
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| 556 | * @param array $values |
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| 557 | * @return PDOStatement |
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| 558 | */ |
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| 559 | public function update($query, array $values) |
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| 565 | |||
| 566 | /** |
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| 567 | * Given a query that has been prepared and an array of values to subsitute |
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| 568 | * into the query, the function will return the result. |
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| 569 | * |
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| 570 | * @param string $query |
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| 571 | * @param array $values |
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| 572 | * @return PDOStatement |
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| 573 | */ |
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| 574 | public function delete($query, array $values) |
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| 580 | |||
| 581 | /** |
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| 582 | * Given a query that has been prepared and an array of optional |
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| 583 | * parameters, this function will return the results of a query |
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| 584 | * as an array. |
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| 585 | * |
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| 586 | * @param string $query |
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| 587 | * @param array $params |
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| 588 | * - `fetch-type` = 'ASSOC'/'OBJECT' |
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| 589 | * Return result as array or an object |
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| 590 | * - `index` = 'column_name' |
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| 591 | * The name of a column in the table to use it's value to index |
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| 592 | * the result by. If this is omitted (and it is by default), an |
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| 593 | * array of associative arrays is returned, with the key being the |
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| 594 | * column names |
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| 595 | * `offset` = `0` |
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| 596 | * An integer representing the row to return |
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| 597 | * @return array |
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| 598 | */ |
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| 599 | public function fetch($query = null, array $params = array(), array $values = array()) |
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| 623 | |||
| 624 | /** |
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| 625 | * Takes an SQL string and creates a prepared statement. |
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| 626 | * |
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| 627 | * @link http://php.net/manual/en/pdo.prepare.php |
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| 628 | * @param string $query |
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| 629 | * @param array $driver_options |
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| 630 | * This array holds one or more key=>value pairs to set attribute values |
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| 631 | * for the DatabaseStatement object that this method returns. |
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| 632 | * @return DatabaseStatement |
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| 633 | */ |
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| 634 | public function prepare($query, array $driver_options = array()) |
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| 640 | |||
| 641 | /** |
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| 642 | * Create a transaction. |
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| 643 | * |
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| 644 | * @return DatabaseTransaction |
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| 645 | */ |
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| 646 | public function transaction() |
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| 650 | |||
| 651 | /** |
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| 652 | * Given a query that has been prepared and an array of values to subsitute |
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| 653 | * into the query, the function will return the result. Unlike `insert` and |
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| 654 | * `update`, this function is a bit of a catch all and will be able to populate |
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| 655 | * `$this->_lastResult` with an array of data. This function is usually used |
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| 656 | * via `fetch()`. |
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| 657 | * |
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| 658 | * @see fetch() |
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| 659 | * @param string $query |
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| 660 | * @param array $params |
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| 661 | * Supports `fetch-type` and `offset` parameters for the moment |
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| 662 | * @param array $values |
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| 663 | * If the `$query` has placeholders, this parameter will include the data |
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| 664 | * to subsitute into the placeholders |
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| 665 | * @return boolean |
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| 666 | */ |
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| 667 | public function query($query, array $params = array(), array $values = array()) |
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| 707 | |||
| 708 | /** |
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| 709 | * This function is actually responsible for subsituting the values into |
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| 710 | * the query and logging the query for basic profiling/debugging. |
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| 711 | * |
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| 712 | * @param string $query |
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| 713 | * @param array $values |
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| 714 | * @param boolean $close |
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| 715 | * If true, once the query is executed, the cursor will be closed, |
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| 716 | * otherwise it'll be left open for further manipulation (as done by |
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| 717 | * `query()`). Defaults to `true` |
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| 718 | * @return PDOStatement |
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| 719 | */ |
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| 720 | private function q($query, $values, $close = true) |
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| 765 | |||
| 766 | /** |
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| 767 | * Given an Exception, or called when an error occurs, this function will |
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| 768 | * fire the `QueryExecutionError` delegate and then raise a `DatabaseException` |
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| 769 | * |
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| 770 | * @uses QueryExecutionError |
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| 771 | * @throws DatabaseException |
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| 772 | * @param Exception $ex |
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| 773 | * The exception thrown while doing something with the Database |
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| 774 | * @return void |
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| 775 | */ |
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| 776 | private function error(Exception $ex = null) |
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| 824 | |||
| 825 | /** |
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| 826 | * Throw a new DatabaseException when given an original exception and a query. |
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| 827 | * |
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| 828 | * @param Exception $error |
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| 829 | * @param string $query |
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| 830 | * @param string $query_hash |
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| 831 | */ |
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| 832 | public function throwError(Exception $error, $query, $query_hash) |
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| 839 | |||
| 840 | /** |
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| 841 | * Function is called everytime a query is executed to log it for |
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| 842 | * basic profiling/debugging purposes |
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| 843 | * |
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| 844 | * @uses PostQueryExecution |
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| 845 | * @param string $query |
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| 846 | * @param string $query_hash |
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| 847 | * @param integer $stop |
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| 848 | */ |
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| 849 | public function logQuery($query, $query_hash, $stop) |
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| 898 | |||
| 899 | /** |
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| 900 | * Returns all the log entries by type. There are two valid types, |
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| 901 | * error and debug. If no type is given, the entire log is returned, |
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| 902 | * otherwise only log messages for that type are returned |
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| 903 | * |
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| 904 | * @return array |
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| 905 | * An array of associative array's. Log entries of the error type |
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| 906 | * return the query the error occurred on and the error number and |
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| 907 | * message from MySQL. Log entries of the debug type return the |
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| 908 | * the query and the start/stop time to indicate how long it took |
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| 909 | * to run |
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| 910 | */ |
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| 911 | public function debug($type = null) |
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| 917 | |||
| 918 | /** |
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| 919 | * Returns some basic statistics from the MySQL class about the |
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| 920 | * number of queries, the time it took to query and any slow queries. |
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| 921 | * A slow query is defined as one that took longer than 0.0999 seconds |
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| 922 | * This function is used by the Profile devkit |
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| 923 | * |
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| 924 | * @return array |
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| 925 | * An associative array with the number of queries, an array of slow |
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| 926 | * queries and the total query time. |
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| 927 | */ |
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| 928 | public function getStatistics() |
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| 945 | } |
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| 946 |
Having each class in a dedicated file usually plays nice with PSR autoloaders and is therefore a well established practice. If you use other autoloaders, you might not want to follow this rule.