Can we replace PHP language constructs with our own?
<p>PHP allows you to replace or even re-name PHP's built-in functions using functions such as
<a href="http://php.net/manual/en/function.override-function.php" rel="nofollow"><code>override_function</code></a> and <a href="http://php.net/manual/en/function.rename-function.php" rel="nofollow"><code>rename_function</code></a>.</p>

<p>Can we override the PHP's language constructs like <code>echo</code> and <code>eval</code>?</p>
