up: fix some error for run in php8.4

Author: inhere

Diff for: .github/workflows/php.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: [8.1, 8.2, 8.3]
+        php: [8.1, 8.2, 8.3, 8.4]
 #        os: [ubuntu-latest, macOS-latest] # windows-latest,
 
     steps:

Diff for: composer.json

@@ -20,7 +20,7 @@
     }
   ],
   "require": {
-    "php": ">=8.0",
+    "php": ">=8.1",
     "ext-mbstring": "*"
   },
   "require-dev": {

Diff for: src/Str/Traits/StringTruncateHelperTrait.php

@@ -128,7 +128,7 @@ public static function after(string $s, string $sub, string $fallback = ''): str
      *
      * @return bool|string
      */
-    public static function substr(string $str, int $start, int $length = null, string $encoding = 'utf-8'): bool|string
+    public static function substr(string $str, int $start, int|null $length = null, string $encoding = 'utf-8'): bool|string
     {
         if (function_exists('mb_substr')) {
             return mb_substr($str, $start, $length ?? self::strlen($str), $encoding);
@@ -147,7 +147,7 @@ public static function substr(string $str, int $start, int $length = null, strin
      *
      * @return string
      */
-    public static function utf8SubStr(string $str, int $start = 0, int $length = null): string
+    public static function utf8SubStr(string $str, int $start = 0, int|null $length = null): string
     {
         if (empty($str)) {
             return '';
@@ -241,7 +241,7 @@ public static function truncate(string $str, int $maxLength, string $suffix = '.
      *
      * @return string
      */
-    public static function truncate2(string $str, int $start, int $length = null): string
+    public static function truncate2(string $str, int $start, ?int $length = null): string
     {
         if (!$length) {
             $length = $start;