<?
echo "all combination\n";

function printAllCombinationsRecursive($prefix, $levelsLeft) {
  if ($levelsLeft==0)
    echo $prefix . '\n';
  else
    foreach ($letter in array={'a','b','c','d'}) {
      printAllCombinationsRecursive($prefix.$letter,$levelsLeft-1);
    }
}
function printAllCombinationsUpToLength($levels) {
  for ($i=1 $i<$levels; $i++} {
    printAllCombinationsRecursive("",$i);
  }
}
printAllCombinationsUpToLength(24);