Ubuntu 12.04.
Apache, php5, mysql, php5-mysql, mysql-server mysql-client are installed on it.
In general, localhost is fully operational. File system - var folder - www folder (folders with sites are stored in it). If I install Joomla in the www folder, then everything is installed, all settings are supported. If I create folders with sites in the www folder and try to install Jumla into one of them, say, the mysite folder, then JSON is not supported.
Yes, the installer writes that
You can continue the installation, after which the configuration will be shown at the end. You will need to perform another additional step - download the code manually. Click on the next field to highlight all the displayed code, copy it and paste it as a new file and name it configuration.php, then upload this file to your server in the root directory of the site.
But I would like from the very beginning how to install it. How to solve it?