Question

I have written a database class(es) sometime ago, I use this for most projects and recently extended the class to work with transactions.

The Transaction class below does not seem to work correctly, the server is MySQL innoDB and I’ve checked that transactions work on my database(with PHPMyAdmin). So this is obviously an error in my code or my misunderstanding.

<?php

/**
 * Description of Database
 *
 * @author http://stackoverflow.com/users/820750/gerve
 */
class Database {

    private $connection;

    public function __construct($dbServer, $dbName, $dbUser, $dbPassword) {
        $this->connection = mysql_connect($dbServer, $dbUser, $dbPassword);
        mysql_select_db($dbName, $this->connection);
    }

    public function query($query, $die = true) {
        return new Query($query, $this->connection, $die);
    }

    public function escape($param) {
        return mysql_real_escape_string($param, $this->connection);
    }

    public function transaction() {
        return new Transaction($this->connection);
    }

}

class Query {

    private $query;
    public $count;
    public $countModified;
    public $queryString;


    public function __construct($query, $link_identifier, $die = true) {
        if($die){
            $this->query = mysql_query($query, $link_identifier) or die(mysql_error());
        }
        else{
            $this->query = mysql_query($query, $link_identifier);
        }

        $this->count = is_resource($this->query) ? mysql_num_rows($this->query) : 0;
        $this->countModified = mysql_affected_rows($link_identifier);

        $this->queryString = $query;
    }

    public function nextRow() {
        return mysql_fetch_object($this->query);
    }

    public function allRows() {
        $array = array();

        while($row = mysql_fetch_object($this->query)){
            $array[] = $row;
        }

        return $row;
    }

}

class Transaction {

    private $connection;
    private $isAlive;

    public function __construct($link_identifier) {
        $this->connection = $link_identifier;
        $this->query("BEGIN");
        $this->isAlive = true;
    }

    public function query($query) {
        if($this->isAlive){
            $q = new Query($query, $this->connection, false);
            if(mysql_error()){
                $this->rollBack();
                return false;
            }
            else{
                return $q;
            }
        }
    }

    public function rollBack() {
        if($this->isAlive){
            $this->query("ROLLBACK");
            $this->isAlive = false;
        }
    }

    public function commit() {
        if($this->isAlive){
            $this->query("COMMIT");
            $this->isAlive = false;
            return true;
        }
        else{
            return false;
        }
    }

}

?>

EDIT – Example usage of classes

$DB = new Database(dbServer, dbName, dbUser, dbPassword);
$transaction = $DB->transaction();

$transaction->query("INSERT INTO myTable `c1`, `c2` VALUES('1', '2')"); //Works
$transaction->query("INSERT INTO jhsdjkag 5dafa 545"); //Fails
$transaction->query("INSERT INTO myTable2 `c1`, `c2` VALUES('3', '4')"); //Works

$transaction->commit();

The above code should not insert any rows into the database, the second query has failed so none should succeed.

My problem is that it doesn’t rollback, always rows are inserted regardless of failing queries.

Answer 1

I Found that there was an error in the code, just in the __construct(). It was pretty simple, I just changed 1 line:

FROM:

public function __construct($link_identifier) {
    $this->connection = $link_identifier;
    $this->query("BEGIN");
    $this->isAlive = true;
}

TO:

public function __construct($link_identifier) {
    $this->connection = $link_identifier;
    $this->isAlive = true;
    $this->query("BEGIN");
}

->isAlive was being set after the first “BEGIN” query, which means BEGIN was never sent.