title: Yii2 migrations. Percentage sign and brackets in table name
body: <p>I browsed the yii2-oauth2-server code on github and encountered interesting syntax in the <a href="https://github.com/Filsh/yii2-oauth2-server/blob/master/migrations/m140501_075311_add_oauth2_server.php#L42" rel="nofollow">migration file</a>. The code in question looks like this:</p>
  
  <pre><code>    $this-&gt;createTable('{{%oauth_clients}}', [
          ...
      ], $tableOptions);
  </code></pre>
  
  <p>Can someone explain the <code>{{%oauth_clients}}</code> part? What does it mean when the table name is enclosed in <code>{{%..}}</code>? The <a href="http://www.yiiframework.com/doc-2.0/guide-db-migrations.html" rel="nofollow">official documentation on migrations</a> says nothing about it and all examples have the "raw" table names like this:</p>
  
  <pre><code>    $this-&gt;createTable('post_tag', [
          ...
      ]);
  </code></pre>
  
  <p>I checked my database and the table was created as if there were no brackets, its name is simply <code>oauth_clients</code>.</p>