trasformazione da array

[boots]

un po' complicato:

<?php
$array= array("12|a", "12|a", "12|a", "16|a", "21|v", "20|s"); 

$out = array();
foreach($array as $s){
   if(!isset($out[(int)$s]))
      $out[(int)$s] = array();
   $out[(int)$s][] = $s;
}
$out2 = array();
foreach($out as $o){
   if(count($o) > 1){
       $out2[] = $o;
   }else{
        $out2[] = $o[0];
   }
}
 print_r($out2);
?>