Function calls and arrays in PHP
<p>Question 1: What is meaning of <code>expr</code> in the following code?</p>

<pre><code> public function getProblem($id) {
        DB::update($this-&gt;_table_name)
                -&gt;set(array('views' =&gt; DB::expr('views + 1')))

                -&gt;where('id', '=', $id)
                -&gt;execute();
$res = DB::select("*")-&gt;from($this-&gt;_table_name)-&gt;where('id', '=', $id)-&gt;execute()-&gt;as_array();
        return $res[0];
    }


/**
*in another class
 */

public static function expr($string)
 {
  return new Database_Expression($string);
 }
</code></pre>

<p>Question 2: What is <code>res</code> doing, and why just <code>res[0]</code>?</p>
