[9.x] Fixes usage of Redis::many() with empty array (#47307)

* Fixes retrieve empty array of keys in Redis

* Apply fixes from StyleCI

---------

Co-authored-by: StyleCI Bot <[email protected]>

Author: nunomaduro

src/Illuminate/Cache/RedisStore.php

@@ -74,6 +74,10 @@ public function get($key)
      */
     public function many(array $keys)
     {
+        if (count($keys) === 0) {
+            return [];
+        }
+
         $results = [];
 
         $values = $this->connection()->mget(array_map(function ($key) {

tests/Integration/Cache/RedisStoreTest.php

@@ -45,4 +45,24 @@ public function testItCanStoreNan()
         $this->assertTrue($result);
         $this->assertNan(Cache::store('redis')->get('foo'));
     }
+
+    public function testItMultipleItemsCanBeSetAndRetrieved()
+    {
+        $store = Cache::store('redis');
+        $result = $store->put('foo', 'bar', 10);
+        $resultMany = $store->putMany([
+            'fizz' => 'buz',
+            'quz' => 'baz',
+        ], 10);
+        $this->assertTrue($result);
+        $this->assertTrue($resultMany);
+        $this->assertEquals([
+            'foo' => 'bar',
+            'fizz' => 'buz',
+            'quz' => 'baz',
+            'norf' => null,
+        ], $store->many(['foo', 'fizz', 'quz', 'norf']));
+
+        $this->assertEquals([], $store->many([]));
+    }
 }