[?] what's the doese param in destroy(class* &i) mean?

[martinuk]

void destroy(class* &i)
{
      delete i;
      i = NULL;
}

class arr[3] = .....  .
./*construction for each element*/

function(arr[0]);

This is working.

-------------version II-----------------

void destroy(class* i)
{
      delete i;
      i = NULL;
}

class arr[3] = .....  .
./*construction for each element*/
destroy(arr[0]);

This is n't working (Runngtime error);

Why? what does magic "&" do?