explain this php code please
<p>I know that <code>$arr = array()</code> creates a new array called <code>$arr</code>, but what is <code>"somearray"</code>? </p>

<pre><code>&lt;?php
     $arr = array("somearray" =&gt; array(6 =&gt; 5, 13 =&gt; 9, "a" =&gt; 42));
     echo $arr["somearray"][6];    
     echo $arr["somearray"][13];   
     echo $arr["somearray"]["a"];  
?&gt;
</code></pre>
