如何在会话到期后修复Zend DbTableGateway读取/销毁无限循环？

Question

I have a Zend\Session Manager with a DbTableGateway to handle sessions. My code is in another SO answer. But whenever the session expires, I get an error Fatal error: Maximum function nesting level of '100' reached, aborting! in [path]\vendor\zendframework\zend-db\src\Sql\AbstractExpression.php on line 40

I found out how to change the xdebug nesting level to 200, but then I reached the 200 limit too.

So I have an infinite loop between DbTableGateway->read() and DbTableGateway->destroy(). I noticed the 2 lines referenced in the error each call the other method, but it's Zend code so I don't want to change it.

It only happens after the session expires, and not when I remove the row containing the session information from the database. When I looked at the table after this occurred, I noticed that the row is still present in the table except for the data column.

id              name            modified    lifetime data
[random string] [session name]  1468587768  1440     -

So it looks like the read() method checks the table for a row containing the id and name, and finds this row, then calls destroy(), which calls read(). How can I fix this?

On a side note, refreshing the page solves the problem for the user, but I don't want to have code that throws an exception at the user and forces them to refresh the page.

Answer 1

This worked for me: create a class that extends DbTableGateway and modify its destroy method to check if a row exists rather than call the read() function. Then use that class instead of DbTableGateway.

So here's the code for the new save handler class:

class MySessionSaveHandler extends DbTableGateway
{
    /**
     * Destroy session
     *
     * @param  string $id
     * @return bool
     */
    public function destroy($id)
    {
        // I removed "read" to prevent an infinite loop, and am using the first line of "read" instead to check if the row exists
        $rows = $this->tableGateway->select([
            $this->options->getIdColumn()   => $id,
            $this->options->getNameColumn() => $this->sessionName,
        ]);

        if (! (bool) $rows) {
            return true;
        }

        return (bool) $this->tableGateway->delete([
            $this->options->getIdColumn()   => $id,
            $this->options->getNameColumn() => $this->sessionName,
        ]);
    }
}

And here's how you replace DbTableGateway:

/* @var $adapter \Zend\Db\Adapter\Adapter */
$adapter = $serviceManager->get('Zend\Db\Adapter\Adapter');
$tableGateway = new TableGateway('mytablename', $adapter);
return new MySessionSaveHandler($tableGateway, new DbTableGatewayOptions());