Using AND as a conditional
<p>I came across a wordpress theme which used the following code:</p>

<pre><code>is_file and include 'file.php';
</code></pre>

<p>I have never seen this before so I was rather confused. It works fine in the particular wordpress theme I'm looking at. But if I just take that line of code and run it on its own it includes the file but also gives me the following notice:</p>

<pre><code>Notice: Use of undefined constant is_file - assumed 'is_file' in (the file path) on line 3
</code></pre>

<p>But if I do this: </p>

<pre><code>is_file('file.php') and include 'file.php';
</code></pre>

<p>It works fine.</p>

<p>Question 1: Why does this work and where can I read more about using "and" as a conditional?</p>

<p>Question 2: Is it bad coding practice? Is it slower? Any risks? Etc.</p>

<p>Question 3: Why does it work in the wordpress theme but not on its own? (Yes, I use the same PHP settings).</p>
