Array how to combine a variable and text [duplicate]

Below is code:

$domainname     = $_POST[domainname];
        array(
                'action' => 'create',
                'domain' => '.website.com',
                'create' => 'Create'
    ));

I need to add variable $domainname to 'domain'.

I try to do somelike this but not working:

    array(
            'action' => 'create',
            'domain' => .$domainname'.website.com',
            'create' => 'Create'
));

Solution 1:

change:

'domain' => .$domainname'.website.com',

To:

'domain' => $domainname.'.website.com',