Get all pipe-delimited words inside of all curly braced expressions in a string

I have a string like this:

$str = "{It|This} part, but also {spin|rotation} the words";

i want to split {It|This} and {spin|rotation} to It, This ,spin,rotation by regular expression.

I need regular expression for this.

$str = "{It|This} part, but also {spin|rotation} the words";
$pattern =''; // need a pttern here
$arr = preg_split($pattern,$str);
print_r($arr);

Explanation :

Using preg_match_all() the content between the { and } are matched and those matches are cycled through via a foreach , exploding the argument by | and then finally doing an implode()

The code..

$str = "{It|This} part, but also {spin|rotation} the words";
preg_match_all('/{(.*?)}/', $str, $matches);
foreach($matches[1] as $v)
{
    $new_val[]=explode('|',$v);
}
echo $new_val=implode(',',call_user_func_array('array_merge',$new_val));

OUTPUT :

It,This,spin,rotation

Demonstration