In PHP, what does echo followed by two single quotes mean?
<p>I am going through someone else's code for a very old site and it has a lot of lines like this:</p>

<pre><code>echo '';
</code></pre>

<p>I am not familiar with PHP, but having quickly gone through a syntax tutorial, it seems that this command would be printing the contents of the single quotes.  However, the single quotes are empty, and there are LOTS of instances like these.</p>

<p>What is the purpose of having these lines, and how did they end up in the code?</p>
