php expression question
<pre><code>function createHash($string) {
    $check1 = $this-&gt;stringToNumber($string, 0x1505, 0x21);
    $check2 = $this-&gt;stringToNumber($string, 0, 0x1003F);

    $factor = 4;
    $halfFactor = $factor/2;

    $check1 &gt;&gt;= $halfFactor;
    $check1 = (($check1 &gt;&gt; $factor) &amp; 0x3FFFFC0 ) | ($check1 &amp; 0x3F);
    $check1 = (($check1 &gt;&gt; $factor) &amp; 0x3FFC00 ) | ($check1 &amp; 0x3FF);
    $check1 = (($check1 &gt;&gt; $factor) &amp; 0x3C000 ) | ($check1 &amp; 0x3FFF);  

    $calc1 = (((($check1 &amp; 0x3C0) &lt;&lt; $factor) | 
                ($check1 &amp; 0x3C)) &lt;&lt; $halfFactor ) | 
                ($check2 &amp; 0xF0F );
    $calc2 = (((($check1 &amp; 0xFFFFC000) &lt;&lt; $factor) |
                ($check1 &amp; 0x3C00)) &lt;&lt; 0xA) | 
                ($check2 &amp; 0xF0F0000 );

    return ($calc1 | $calc2);
}
</code></pre>

<p><strong>>>=</strong> what does this expression stand for? it looks very strange to me. I couldn't find any questions on google.</p>
