PHP: convert date string to Unix timestamp
<p>Given the following strings:</p>

<ul>
<li>01/01/11</li>
<li>1/1/11</li>
<li>1/1/2011</li>
<li>01/1/2011</li>
<li>1-1-2011</li>
<li>etc</li>
</ul>

<p>How do I convert these to a Unix timestamp. Note that in most cases, this will be in the format of <code>dd mm yyyy</code> with various delimiters. </p>
