Drop PHP 5.6 + 7.0 (#257)

* Drop PHP 5.6 + 7.0

* Remove `syntaxCheck`

* Add void

Author: ruudk

Tests/IntegrationTest.php

@@ -28,15 +28,15 @@ class IntegrationTest extends TestCase
      */
     private $cache;
 
-    protected function setUp()
+    protected function setUp(): void
     {
         $cache = new Memcached();
         $cache->addServer('localhost', 11211);
 
         $this->cache = new MemcachedCachePool($cache);
     }
 
-    protected function tearDown()
+    protected function tearDown(): void
     {
         if ($this->cache !== null) {
             $this->cache->clear();

composer.json

@@ -17,13 +17,13 @@
     ],
     "homepage": "http://www.php-cache.com/en/latest/",
     "require": {
-        "php": "^5.6 || ^7.0 || ^8.0",
+        "php": "^7.1 || ^8.0",
         "cache/hierarchical-cache": "^1.0",
         "psr/cache": "^1.0 || ^2.0"
     },
     "require-dev": {
         "cache/memcached-adapter": "^1.0",
-        "phpunit/phpunit": "^5.7.21"
+        "phpunit/phpunit": "^7.5.20 || ^9.5.10"
     },
     "minimum-stability": "dev",
     "prefer-stable": true,

phpunit.xml.dist

@@ -8,7 +8,6 @@
   convertWarningsToExceptions="true"
   processIsolation="false"
   stopOnFailure="false"
-  syntaxCheck="false"
   bootstrap="vendor/autoload.php"
   >
   <testsuites>