<?php
 
$d1 = range("A", "C");
$d2 = range("1", "3");
$d3 = range("X", "Y");
 
$in=array($d1, $d2, $d3);
 
$c = new combo($in);
print_r($c->result);
 
class combo{
  public $items;
  public $result;
 
  function __construct( $items){
    $this->items= $items;
    $result=array();
    $this->expand('', 0);
  }
  function expand( $prefix, $index){
    if ($index==count($this->items)){
      $this->result[]=$prefix;
      return;
    }
    //empty case
    $this->expand($prefix, $index+1);
    //combinate
    foreach($this->items[$index] as $item){
      $this->expand($prefix.$item, $index+1);
    }
 
  }
 
}

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