in php, a function's arguments can be a word without quotes or $
<p>I always thought that the arguments of a function in PHP should be either a string enclosed by '', or a number, or a variable.</p>

<p>However, looking at this in php.net's manual I see:</p>

<pre><code>   public function baz(Test $other)
</code></pre>

<p>What does the word Test here refer to?</p>

<p>How is this possible?</p>
