minor #39775 [WIP] Use ::class keyword when possible (fabpot)

This PR was merged into the 4.4 branch.

Discussion
----------

[WIP] Use ::class keyword when possible

| Q             | A
| ------------- | ---
| Branch?       | 4.4 <!-- see below -->
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tickets       | n/a  <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT
| Doc PR        | n/a

Commits
-------

036a36cb14 Use ::class keyword when possible

Author: fabpot

Tests/Session/SessionTest.php

@@ -89,7 +89,7 @@ public function testSetIdAfterStart()
         } catch (\Exception $e) {
         }
 
-        $this->assertInstanceOf('\LogicException', $e);
+        $this->assertInstanceOf(\LogicException::class, $e);
     }
 
     public function testSetName()

Tests/Session/Storage/Handler/MemcachedSessionHandlerTest.php

@@ -136,6 +136,6 @@ public function testGetConnection()
         $method = new \ReflectionMethod($this->storage, 'getMemcached');
         $method->setAccessible(true);
 
-        $this->assertInstanceOf('\Memcached', $method->invoke($this->storage));
+        $this->assertInstanceOf(\Memcached::class, $method->invoke($this->storage));
     }
 }

Tests/Session/Storage/Handler/PdoSessionHandlerTest.php

@@ -298,7 +298,7 @@ public function testGetConnection()
         $method = new \ReflectionMethod($storage, 'getConnection');
         $method->setAccessible(true);
 
-        $this->assertInstanceOf('\PDO', $method->invoke($storage));
+        $this->assertInstanceOf(\PDO::class, $method->invoke($storage));
     }
 
     public function testGetConnectionConnectsIfNeeded()
@@ -308,7 +308,7 @@ public function testGetConnectionConnectsIfNeeded()
         $method = new \ReflectionMethod($storage, 'getConnection');
         $method->setAccessible(true);
 
-        $this->assertInstanceOf('\PDO', $method->invoke($storage));
+        $this->assertInstanceOf(\PDO::class, $method->invoke($storage));
     }
 
     /**