比较增量字符串

Question

so this is kinda hard to form a question about my issue so just picture what i'm going to explain,

image you have a list of multiple strings that contain characters from A to Z after Z it goes to AA, AB, AC etc etc...

I want to get the highest on the list for that i'm trying to do something like this:

$max_letter = "A";
while($row = mysqli_fetch_assoc($recordset)) {
    if($row["new_letter"] > $max_letter) {
        $max_letter = $row["new_letter"];
    }
}

the problem with this is that when $row["new_letter"] is equal to "AA" and $max_letter is equal to "Z" it doesn't update $max_letter to "AA" because it thinks "Z" is higher than "AA"

but if i do something like this:

$str = "Z";
echo ++$str;

my output will be

AA

example of my problem:

$str = "Z";
echo ++$str;

echo "<br><br>";

if("AA" > "Z") {
    echo "higher";
}elseif("AA" == "Z") {
    echo "equal";   
}elseif("AA" < "Z") {
    echo "lower";
}

Answer 1

this would likely work:

$max_letter = "A";
while($row = mysqli_fetch_assoc($recordset)) {
    if(cvrt($row["new_letter"]) > cvrt($max_letter)) {
        $max_letter = $row["new_letter"];
    }
}

function cvrt(incStr){
    $ret = "";
    foreach(str_split(incStr) as $v){
        $ret .= ord($v);
    }
    return $ret;
}

not pretty but I think it will work for any length of string.

what you are doing here is concatenating the numerical values of the letters in the string and returning them to be compared as a number.