<%    
      
   $ONE = "one";
   $TWO = "TWO";
      
   function test () 
   { 
      $f = array ('ONE', 'TWO'); 
      for ($i = 0; $i < count ($f); ++$i) { 
         GLOBAL ${$f[$i]};  // this line produces parse err
//	 GLOBAL $$f[$i]; // parses OK and is OK.
         print "<p>" . ${$f[$i]} . "\n"; 
      }       
   } 
     
   test ();
     
%>   
May be a documentation error. Cf. http://www.php3.de/manual/variable-variable.php3

"In order to use variable variables with arrays, you have to resolve an ambiguity problem. That is, if you write $$a[1] then the parser needs to know if you meant to use $a[1] as a variable, or if you wanted $$a as the variable and then the [1] index from that variable. The syntax for resolving this ambiguity is: ${$a[1]} for the first case and ${$a}[1] for the second"