RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . index.php

....
            'urlManager' => [
            'enablePrettyUrl' => true,
             'showScriptName' => false,
             'suffix'=>'/',
             'rules'=>array(
                 ''=>'site/index',
                 '<action>'=>'site/<action>',
             ),
        ],
...

'urlManager'=>array(
  'urlFormat'=>'path',
  'rules'=>array(
  '<action:\w+>'=>'<controller>/<action>',
  ),
),