Swoole 6: bump minimum supported PHP version to 8.1

.github/workflows/coding_style_checks.yml

@@ -11,4 +11,4 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run Coding Style Checks
-        run: docker run -q --rm -v "$(pwd):/project" -w /project -i jakzal/phpqa:php8.2-alpine php-cs-fixer fix --dry-run
+        run: docker run -q --rm -v "$(pwd):/project" -w /project -i jakzal/phpqa:php8.1-alpine php-cs-fixer fix --dry-run

.github/workflows/syntax_checks.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        php: ["8.0", "8.1", "8.2", "8.3"]
+        php: ["8.1", "8.2", "8.3"]
 
     name: Syntax Checks Under PHP ${{ matrix.php }}
 

src/swoole/Swoole/Redis/Server.php

@@ -85,7 +85,7 @@ public function setHandler(string $command, callable $callback): bool
     /**
      * @return callable|null Returns the callback function if defined, otherwise NULL.
      */
-    public function getHandler(string $command): callable|null
+    public function getHandler(string $command): ?callable
     {
     }