// Bug-script for assigning references for global variables inside functions
  $fruit = "apple";
  $rock = "granite";

  function twiddle(){
    global $fruit, $rock;
    $fruit = &$rock;

    $GLOBALS["rock"] = &$GLOBALS["fruit"]; 

    // the "global" command works here
    echo "inside : fruit=$fruit rock=$rock<br>\n";

  }

  echo "BEFORE: fruit=$fruit  rock=$rock<br>";
  twiddle();
  echo "AFTER: fruit=$fruit  rock=$rock";
  // But only the reassignment using GLOBALS has an effect outside
  // the function; the "global" assignment  persists only inside.

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PHP configured with mysql ; otherwise plain vanilla.