Number to Excel column name conversion

In Excel, column names are characters from A to Z, if there are more columns needed, it continues with AA, AB ...

I want to write a function, that converts integers to those excel column names.

0 .... A
25 ... Z
26 ... AA

The solution I came up with is working up to AZ, but I want it to work further.

function indexToXlxsColumn($index, $prefix="")
{
    if($index < 26)
    {
        return $prefix.chr($index+65);
    }else{
        return indexToXlxsColumn($index % 26, "A");
    }
}

How to adapt this function to work for each index without producing spaghetti code?