Added registration and requirement check functions;

Moved previous factory checks into those new methods, with SHM automatically registering the bundled adapters;
Avoided the APC errors by checking for the extension before its version.

Author: boenrobot

src/PEAR2/Cache/SHM.php

@@ -20,11 +20,6 @@
  */
 namespace PEAR2\Cache;
 
-/**
- * Calls adapters. 
- */
-use PEAR2\Cache\SHM\Adapter;
-
 /**
  * Main class for this package.
  * 
@@ -38,6 +33,10 @@
  */
 abstract class SHM implements \IteratorAggregate
 {
+    /**
+     * @var array An array of adapter names that meet their requirements.
+     */
+    private static $_adapters = array();
 
     /**
      * Creates a new shared memory storage.
@@ -47,21 +46,54 @@ abstract class SHM implements \IteratorAggregate
      * 
      * @param string $persistentId The ID for the storage.
      * 
-     * @return self|SHM A new instance of an SHM adapter (child of this class).
+     * @return static|SHM A new instance of an SHM adapter (child of this
+     * class).
      */
     public static function factory($persistentId)
     {
-        if ('cli' === PHP_SAPI) {
-            return new Adapter\Placebo($persistentId);
-        } elseif (version_compare(phpversion('wincache'), '1.1.0', '>=')) {
-            return new Adapter\Wincache($persistentId);
-        } elseif (version_compare(phpversion('apc'), '3.0.13', '>=')) {
-            return new Adapter\APC($persistentId);
-        } else {
-            throw new SHM\InvalidArgumentException(
-                'No appropriate adapter available', 1
-            );
+        foreach (self::$_adapters as $adapter) {
+            try {
+                return new $adapter($persistentId);
+            } catch (\Exception $e) {
+            }
+        }
+        throw new SHM\InvalidArgumentException(
+            'No appropriate adapter available', 1
+        );
+    }
+    
+    /**
+     * Checks if the adapter meets its requirements.
+     * 
+     * @return bool TRUE on success, FALSE on failure.
+     */
+    abstract public static function isMeetingRequirements();
+    
+    /**
+     * Registers an adapter.
+     * 
+     * Registers an SHM adapter, allowing you to call it with {@link factory()}.
+     * 
+     * @param string $adapter FQCN of adapter. A valid adapter is one that
+     * extends this class.
+     * @param bool   $prepend Whether to prepend this adapter into the list of
+     * possible adapters, instead of appending to it.
+     * 
+     * @return bool TRUE on success, FALSE on failure.
+     */
+    public static function registerAdapter($adapter, $prepend = false)
+    {
+        if (is_subclass_of($adapter, '\\' . __CLASS__)
+            && $adapter::isMeetingRequirements()
+        ) {
+            if ($prepend) {
+                self::$_adapters = array_merge(array($adapter), self::$_adapters);
+            } else {
+                self::$_adapters[] = $adapter;
+            }
+            return true;
         }
+        return false;
     }
 
     /**
@@ -272,4 +304,13 @@ abstract public function cas($key, $old, $new);
      * @return void
      */
     abstract public function clear();
-}
+}
+
+foreach (
+    array('\Adapter\APC', '\Adapter\Placebo', '\Adapter\Wincache') as $adapter
+) {
+    if (class_exists($adapter = '\\' . __NAMESPACE__ . $adapter, true)) {
+        SHM::registerAdapter($adapter);
+    }
+}
+unset($adapter);

src/PEAR2/Cache/SHM/Adapter/APC.php

@@ -81,6 +81,17 @@ public function __construct($persistentId)
         );
     }
 
+    /**
+     * Checks if the adapter meets its requirements.
+     * 
+     * @return bool TRUE on success, FALSE on failure.
+     */
+    public static function isMeetingRequirements()
+    {
+        return extension_loaded('apc')
+            && version_compare(phpversion('apc'), '3.0.13', '>=');
+    }
+    
     /**
      * Releases all locks in a storage.
      * 

src/PEAR2/Cache/SHM/Adapter/Placebo.php

@@ -18,7 +18,6 @@
 /**
  * The namespace declaration.
  */
-
 namespace PEAR2\Cache\SHM\Adapter;
 
 /**
@@ -102,6 +101,16 @@ public function __destruct()
         }
     }
 
+    /**
+     * Checks if the adapter meets its requirements.
+     * 
+     * @return bool TRUE on success, FALSE on failure.
+     */
+    public static function isMeetingRequirements()
+    {
+        return 'cli' === PHP_SAPI;
+    }
+    
     /**
      * Pretends to obtain a lock.
      * 

src/PEAR2/Cache/SHM/Adapter/Wincache.php

@@ -18,7 +18,6 @@
 /**
  * The namespace declaration.
  */
-
 namespace PEAR2\Cache\SHM\Adapter;
 
 /**
@@ -96,6 +95,17 @@ protected static function encodeLockName($name)
         return str_replace(array('%', '\\'), array('%25', '%5C'), $name);
     }
 
+    /**
+     * Checks if the adapter meets its requirements.
+     * 
+     * @return bool TRUE on success, FALSE on failure.
+     */
+    public static function isMeetingRequirements()
+    {
+        return extension_loaded('wincache')
+            && version_compare(phpversion('wincache'), '1.1.0', '>=');
+    }
+    
     /**
      * Releases any locks obtained by this instance as soon as there are no more
      * references to the object's persistent ID.

tests/PHPT/SHM-factory_CGI.phpt

@@ -7,7 +7,4 @@ Checks that SHM::factory() can be called from the command line.
 
 --FILE_EXTERNAL--
 SHM-factory.inc
---XFAIL--
-Odd startup PCNTL related errors coming from APC...
-just for this test for some reason.
 --EXPECT--