minor symfony#18992 [Cache] AbstractAdapter: avoid an extra call to ApcuAdapter::isSupported (dunglas)

This PR was squashed before being merged into the 3.2-dev branch (closes symfony#18992).

Discussion
----------

[Cache] AbstractAdapter: avoid an extra call to ApcuAdapter::isSupported

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? |  no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

8f2ea52 [Cache] AbstractAdapter: avoid an extra call to ApcuAdapter::isSupported

Author: fabpot

src/Symfony/Component/Cache/Adapter/AbstractAdapter.php

@@ -24,6 +24,9 @@ abstract class AbstractAdapter implements AdapterInterface, LoggerAwareInterface
 {
     use LoggerAwareTrait;
 
+    private static $apcuSupported;
+    private static $phpFilesSupported;
+
     private $namespace;
     private $deferred = array();
     private $createCacheItem;
@@ -70,7 +73,15 @@ function ($deferred, $namespace, &$expiredIds) {
 
     public static function createSystemCache($namespace, $defaultLifetime, $version, $directory, LoggerInterface $logger = null)
     {
-        if (!ApcuAdapter::isSupported() && PhpFilesAdapter::isSupported()) {
+        if (null === self::$apcuSupported) {
+            self::$apcuSupported = ApcuAdapter::isSupported();
+        }
+
+        if (!self::$apcuSupported && null === self::$phpFilesSupported) {
+            self::$phpFilesSupported = PhpFilesAdapter::isSupported();
+        }
+
+        if (self::$phpFilesSupported) {
             $opcache = new PhpFilesAdapter($namespace, $defaultLifetime, $directory);
             if (null !== $logger) {
                 $opcache->setLogger($logger);
@@ -83,7 +94,7 @@ public static function createSystemCache($namespace, $defaultLifetime, $version,
         if (null !== $logger) {
             $fs->setLogger($logger);
         }
-        if (!ApcuAdapter::isSupported()) {
+        if (!self::$apcuSupported) {
             return $fs;
         }