Always return the same instance of a const

Implement EnumManager to keep track of all instances

src/Enum.php

@@ -165,6 +165,21 @@ public static function search($value)
         return array_search($value, static::toArray(), true);
     }
 
+    /**
+     * Returns Enum by key
+     *
+     * @return static
+     */
+    public static function fromKey($name)
+    {
+        $array = static::toArray();
+        if (array_key_exists($name, $array)) {
+            return EnumManager::get(new static($array[$name]));
+        }
+
+        return null;
+    }
+
     /**
      * Returns a value when called statically like so: MyEnum::SOME_VALUE() given SOME_VALUE is a class constant
      *
@@ -176,11 +191,12 @@ public static function search($value)
      */
     public static function __callStatic($name, $arguments)
     {
-        $array = static::toArray();
-        if (isset($array[$name])) {
-            return new static($array[$name]);
+        $result = static::fromKey($name);
+
+        if ($result === null) {
+            throw new \BadMethodCallException("No static method or enum constant '$name' in class " . get_called_class());
         }
 
-        throw new \BadMethodCallException("No static method or enum constant '$name' in class " . get_called_class());
+        return $result;
     }
 }

src/EnumManager.php

@@ -0,0 +1,43 @@
+<?php
+/**
+ * @link    http://github.com/myclabs/php-enum
+ * @license http://www.opensource.org/licenses/mit-license.php MIT (see the LICENSE file)
+ */
+
+namespace MyCLabs\Enum;
+
+use ReflectionObject;
+
+/**
+ * Enum instance manager
+ *
+ * @internal
+ */
+abstract class EnumManager
+{
+    /**
+     * Store existing Enum instances.
+     *
+     * @var array
+     */
+    private static $instances = array();
+
+    /**
+     * Returns the Enum instance for the given prototype
+     *
+     * @return Enum
+     */
+    public static function get(Enum $enum)
+    {
+        $reflection = new ReflectionObject($enum);
+        $class = $reflection->getName();
+        $name = $enum->getKey();
+
+        if (isset(self::$instances[$class][$name])) {
+            return self::$instances[$class][$name];
+        }
+
+        self::$instances[$class][$name] = $enum;
+        return $enum;
+    }
+}

tests/EnumTest.php

@@ -228,6 +228,17 @@ public function testEquals()
         $this->assertTrue($foo->equals($anotherFoo));
     }
 
+    /**
+     * __callStatic()
+     */
+    public function testSameInstance()
+    {
+        $foo1 = EnumFixture::FOO();
+        $foo2 = EnumFixture::FOO();
+
+        $this->assertSame($foo1, $foo2);
+    }
+
     /**
      * equals()
      */