php variable name and braces
<p>A similar question was asked here: <a href="http://stackoverflow.com/questions/2690858/php-variable-like-myvar-test-is-not-valid">PHP variable like $myvar-test is not valid?</a></p>

<p>And I've read the <a href="http://www.php.net/manual/en/userlandnaming.php" rel="nofollow">PHP Userland Naming Guide</a>
Where it says:</p>

<blockquote>
  <blockquote>
    <p>Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'</p>
  </blockquote>
</blockquote>

<p>What I'm curious about is this <a href="http://stackoverflow.com/a/2690951/671191">answer</a> , and why these workarounds work: <code>${'0x00'}</code>, or this: <code>${'900'}</code>, or this <code>${'bad-name'}</code>. </p>

<p>My question has two parts... why does this work? The second part of my question: Would they be considered valid variables or would be considered something else (I'm not asking if they work, but what they would be classified as.)</p>
