php for "high-traffic" websites
<p>I have read that PHPs "probable" weakness is how it handles "concurrency". With only sessions and cookies to keep track of user state, how can PHP handle the following situations with high accuracy:</p>

<ol>
<li><p>multiple users check out with one item that has only 1 stock in inventory (sorry for grammar mistakes, but you pretty much get the picture already)</p></li>
<li><p>multiple users logging into the same user account using the same login details</p></li>
<li><p>multiple users editing an the same image at the same time (though this rarely happens in real life)</p></li>
</ol>

<p>or any other transactions that demands multiple thread handling</p>

<p>(I apologize if I misused terms here)</p>
