title: What does "*RECURSION*" mean when printing $GLOBALS?
body: <p>When I print <code>$GLOBALS</code> using this code:</p>
  
  <pre><code>&lt;?php print_r($GLOBALS); ?&gt;
  </code></pre>
  
  <p>I get this output:</p>
  
  <p><code>Array ( [_GET] =&gt; Array ( ) [_POST] =&gt; Array ( ) [_COOKIE] =&gt; Array ( ) [_FILES] =&gt; Array ( ) [GLOBALS] =&gt; Array *RECURSION* )</code></p>
  
  <p>What does "<code>*RECURSION*</code>" mean in this case, and why are <code>$_SERVER</code>, <code>$_REQUEST</code>, etc. not printed as well?</p>