What is the php equivalent for Encoding.ASCII.GetBytes(vstrEncryptionKey.ToCharArray())
<p>What is the PHP equivalent for  the following C# code</p>

<pre><code>Encoding.ASCII.GetBytes(vstrEncryptionKey.ToCharArray())
</code></pre>

<p>where <code>vstrEncryptionKey</code> is a variable?</p>
