What purpose does empty exception class serve?
<p>I have seen implementation for exceptions like:</p>

<pre><code>&lt;?php

class TestE extends Exception {}

class MyTest {

    public function __construct() {
        try{
            throw new TestE('This is an exception!');
        }catch(Exception $exc){
            var_dump($exc);
        }

        echo '2';
    }
}

$o = new MyTest();
</code></pre>

<p>where a custom exception class like <code>TestE</code> is defined but kept empty as above. What purpose does it achieve? I could have easily used:</p>

<pre><code>throw new Exception('This is an exception')
</code></pre>

<p>instead of </p>

<pre><code>throw new TestE('This is an exception')
</code></pre>