Why is ${0x0} correct?
<p>The following code is working perfectly:</p>

<pre><code>${0x0} = 'test';
echo ${0x0}; // prints "test"
</code></pre>

<p>But I can't figure out why. <code>0x0</code> (or <code>0</code>, as non-hex people call it) is a random container, it could have been any number, but php variables can't start with a number. What's so special about the <code>{ }</code> used here, and what are their limitations ?</p>
