a function to get column index by letter
function getColumnNumber($char){
$alphabet = range('a','z');
$alphabet2 = range('a','z');
$newAlphabet = $alphabet;
foreach($alphabet as $k => $r)
{
foreach($alphabet2 as $row){
$newAlphabet[] = $r.$row;
}
}
$key = array_search($char, $newAlphabet);
return ($key !== false) ? $key : null;
}