each() doesn't reset an array's internal pointer to the first element after executing, which can cause a lot of headaches if you expect that to be the case...  I don't know if this is intentional or an oversight, and I can imagine it being either one.

For instance:
<?
echo "<pre>firstpass\n\n";
while ( list( $k, $v ) = each( $GLOBALS ) ) { echo "\n$k => $v"; }
echo "\n\nsecondpass";
while ( list( $k, $v ) = each( $GLOBALS ) ) { echo "\n$k => $v"; }
?>

Will output this to the browser:

  firstpass

  GLOBALS => 
  HTTP_GET_VARS => Array
  HTTP_COOKIE_VARS => Array
  INIT_VERSION => sysvinit-2.69
  TERM => linux
  etc....

  secondpass
  <i>nothing at all...</i>

Of course this can be fixed by adding a call to reset($somearray) after each call to each($somearray), but that doesn't seem very intuitive.