Fix getting option value from configuration

Configuration tries to read ['value'] from an array but it throws a PHP Warning:  Illegal string offset 'value'.

Configuration file containing
```
<options>
    <option id="PDO::MYSQL_ATTR_INIT_COMMAND">SET NAMES utf8</option>
</options>
```

Generates the following PHP configuration file:
```
'options' =>
  array (
    'PDO::MYSQL_ATTR_INIT_COMMAND' => 'SET NAMES utf8',
  ),
```