PHP - loop through letters

Question

I am trying to loop through letters rather than numbers.

I am trying to do this using chr and the number equivalent but it doesn\'t seem to be happening!

I want

Answer 1

for( $x = "AAAA"; ; $x++) {
    echo $x."\n";
    if( $x == "ZZZZ") break;
}

Incrementing a letter will cycle it through the alphabet similar to the column names in Excel.