# db2_rollback

(PECL ibm_db2 >= 1.0.0)

db2_rollback — Rolls back a transaction

### 说明

db2_rollback ( resource `$connection` ) : bool

Rolls back an in-progress transaction on the specified connection resource and begins a new transaction. PHP applications normally default to AUTOCOMMIT mode, so db2_rollback() normally has no effect unless AUTOCOMMIT has been turned off for the connection resource.

### 参数

`connection`

  A valid database connection resource variable as returned from db2_connect() or db2_pconnect().

### 返回值

成功时返回 `TRUE`， 或者在失败时返回 `FALSE`。

### 范例

Example #1 Rolling back a DELETE statement

In the following example, we count the number of rows in a table, turn off AUTOCOMMIT mode on a database connection, delete all of the rows in the table and return the count of 0 to prove that the rows have been removed. We then issue db2_rollback() and return the updated count of rows in the table to show that the number is the same as before we issued the DELETE statement. The return to the original state of the table demonstrates that the roll back of the transaction succeeded.

    <?php
    $conn = db2_connect($database, $user, $password);

    if ($conn) {
        $stmt = db2_exec($conn, "SELECT count(*) FROM animals");
        $res = db2_fetch_array( $stmt );
        echo $res[0] . "\n";

        // Turn AUTOCOMMIT off
        db2_autocommit($conn, DB2_AUTOCOMMIT_OFF);

        // Delete all rows from ANIMALS
        db2_exec($conn, "DELETE FROM animals");

        $stmt = db2_exec($conn, "SELECT count(*) FROM animals");
        $res = db2_fetch_array( $stmt );
        echo $res[0] . "\n";

        // Roll back the DELETE statement
        db2_rollback( $conn );

        $stmt = db2_exec( $conn, "SELECT count(*) FROM animals" );
        $res = db2_fetch_array( $stmt );
        echo $res[0] . "\n";
        db2_close($conn);
    }
    ?>

以上例程会输出：

    7
    0
    7

### 参见

- db2_autocommit() - Returns or sets the AUTOCOMMIT state for a database connection
- db2_commit() - Commits a transaction