diff --git a/phpBB/includes/acm/acm_apc.php b/phpBB/includes/acm/acm_apc.php
index ff24dfa0d8..1a487f94ad 100644
--- a/phpBB/includes/acm/acm_apc.php
+++ b/phpBB/includes/acm/acm_apc.php
@@ -19,7 +19,7 @@ if (!defined('IN_PHPBB'))
 // Include the abstract base
 if (!class_exists('acm_memory'))
 {
-	require("${phpbb_root_path}includes/acm/acm_memory.$phpEx");
+	require("{$phpbb_root_path}includes/acm/acm_memory.$phpEx");
 }
 
 /**
@@ -30,12 +30,6 @@ class acm extends acm_memory
 {
 	var $extension = 'apc';
 
-	function acm()
-	{
-		// Call the parent constructor
-		parent::acm_memory();
-	}
-
 	/**
 	* Purge cache data
 	*
diff --git a/phpBB/includes/acm/acm_eaccelerator.php b/phpBB/includes/acm/acm_eaccelerator.php
index 7530043e83..1a3cf3c0f7 100644
--- a/phpBB/includes/acm/acm_eaccelerator.php
+++ b/phpBB/includes/acm/acm_eaccelerator.php
@@ -19,7 +19,7 @@ if (!defined('IN_PHPBB'))
 // Include the abstract base
 if (!class_exists('acm_memory'))
 {
-	require("${phpbb_root_path}includes/acm/acm_memory.$phpEx");
+	require("{$phpbb_root_path}includes/acm/acm_memory.$phpEx");
 }
 
 /**
@@ -33,12 +33,6 @@ class acm extends acm_memory
 
 	var $serialize_header = '#phpbb-serialized#';
 
-	function acm()
-	{
-		// Call the parent constructor
-		parent::acm_memory();
-	}
-
 	/**
 	* Purge cache data
 	*
diff --git a/phpBB/includes/acm/acm_memcache.php b/phpBB/includes/acm/acm_memcache.php
index b22205578e..5a34a2a51d 100644
--- a/phpBB/includes/acm/acm_memcache.php
+++ b/phpBB/includes/acm/acm_memcache.php
@@ -19,7 +19,7 @@ if (!defined('IN_PHPBB'))
 // Include the abstract base
 if (!class_exists('acm_memory'))
 {
-	require("${phpbb_root_path}includes/acm/acm_memory.$phpEx");
+	require("{$phpbb_root_path}includes/acm/acm_memory.$phpEx");
 }
 
 if (!defined('PHPBB_ACM_MEMCACHE_PORT'))
diff --git a/phpBB/includes/acm/acm_xcache.php b/phpBB/includes/acm/acm_xcache.php
index 9cb8eae272..ad527b8220 100644
--- a/phpBB/includes/acm/acm_xcache.php
+++ b/phpBB/includes/acm/acm_xcache.php
@@ -19,7 +19,7 @@ if (!defined('IN_PHPBB'))
 // Include the abstract base
 if (!class_exists('acm_memory'))
 {
-	require("${phpbb_root_path}includes/acm/acm_memory.$phpEx");
+	require("{$phpbb_root_path}includes/acm/acm_memory.$phpEx");
 }
 
 /**
@@ -30,12 +30,6 @@ class acm extends acm_memory
 {
 	var $extension = 'xcache';
 
-	function acm()
-	{
-		// Call the parent constructor
-		parent::acm_memory();
-	}
-
 	/**
 	* Purge cache data
 	*
@@ -62,7 +56,9 @@ class acm extends acm_memory
 	*/
 	function _read($var)
 	{
-		return xcache_get($this->key_prefix . $var);
+		$result = xcache_get($this->key_prefix . $var);
+
+		return ($result !== null) ? $result : false;
 	}
 
 	/**
@@ -100,7 +96,6 @@ class acm extends acm_memory
 	*/	
 	function _isset($var)
 	{
-		// Most caches don't need to check
 		return xcache_isset($this->key_prefix . $var);
 	}
 }