php字符串增加1怎么实现

<?php
 
function inc($s) {
    if (empty($s)) {return "1";}
    if ( ! isset($s[1]) ) {
        $code = ord($s[0]) + 1;
        if ($code <= ord("9")) {
            return chr($code);
        }
        return "10";
    }
    $n = strlen($s);
    $code = ord($s[$n-1]) +1;
    if ($code <= ord("9")) {
        return substr($s, 0, $n-1).chr($code);
    }
    return inc(substr($s, 0, $n-1))."0";
}
 
$s = "2147483647";
$n = 10000;
while ($n-- > 0) {
    // printf("%s\n", $s);
    $s = inc($s);
}
printf("%s\n", $s); // "2147493647"

<?php
 
$m = 2147483647;
 
$n = 10000;
while ($n-- > 0) {
    // printf("%d\n", $m);
    $m++;
}
printf("%d\n", $m);

<?php
 
function add($s) {
    if (empty($s)) {return "A";}
    if ( ! isset($s[1]) ) {
        $code = ord($s[0]) + 1;
        if ($code <= ord("Z")) {
            return chr($code);
        }
        return "AA";
    }
    $n = strlen($s);
    $code = ord($s[$n-1]) +1;
    if ($code <= ord("Z")) {
        return substr($s, 0, $n-1).chr($code);
    }
    return add(substr($s, 0, $n-1))."A";
}
 
$s = "";
do {
    $s = add($s);
    printf("%s\n", $s);
} while ($s != "ZZZZ");