PHP/MySQL Critical section -


i'm using php pdo , innodb tables.

i want code allow 1 user-submitted operation complete, user can either cancel or complete. in case user posts both operations, want 1 of requests fail , rollback, isn't happening right now, both completing without exception/error. thought deleting row after checking exists enough.

$pdo = new pdo();  try {      $pdo->begintransaction();      $rowcheck = $pdo->query("select * table id=99")->rowcount();      if ($rowcheck == 0)         throw new runtimeexception("row isn't there");      $pdo->exec("delete table id = 99");      // either cancel, 1 bunch of queries. if (isset($_post['cancel'])) ...     // or complete, bunch of queries. if (isset($_post['complete'])) ...     // bunch of queries on other tables here...      $pdo->commit();  } catch (exception $e) {      $pdo->rollback();      throw $e;  }

how can make cancel / complete operations critical section? second operation must fail.

the code fine, 1 exception: add for update initial select. should suffice block second button press until first delete has happened, thereby leading second 1 "failing".

https://dev.mysql.com/doc/refman/5.5/en/innodb-locking-reads.html

note locking of rows update using select update applies when autocommit disabled (either beginning transaction start transaction or setting autocommit 0. if autocommit enabled, rows matching specification not locked.


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