diff --git a/phpBB/includes/acp/acp_inactive.php b/phpBB/includes/acp/acp_inactive.php
index 66f0d2116c..4ee4cd4816 100644
--- a/phpBB/includes/acp/acp_inactive.php
+++ b/phpBB/includes/acp/acp_inactive.php
@@ -24,9 +24,9 @@ class acp_inactive
 	var $u_action;
 	var $p_master;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/acp/acp_permissions.php b/phpBB/includes/acp/acp_permissions.php
index 8e05b95849..e683b1972e 100644
--- a/phpBB/includes/acp/acp_permissions.php
+++ b/phpBB/includes/acp/acp_permissions.php
@@ -676,7 +676,7 @@ class acp_permissions
 	/**
 	* Apply permissions
 	*/
-	function set_permissions($mode, $permission_type, &$auth_admin, &$user_id, &$group_id)
+	function set_permissions($mode, $permission_type, $auth_admin, &$user_id, &$group_id)
 	{
 		global $db, $cache, $user, $auth;
 		global $request;
@@ -765,7 +765,7 @@ class acp_permissions
 	/**
 	* Apply all permissions
 	*/
-	function set_all_permissions($mode, $permission_type, &$auth_admin, &$user_id, &$group_id)
+	function set_all_permissions($mode, $permission_type, $auth_admin, &$user_id, &$group_id)
 	{
 		global $db, $cache, $user, $auth;
 		global $request;
@@ -881,7 +881,7 @@ class acp_permissions
 	/**
 	* Remove permissions
 	*/
-	function remove_permissions($mode, $permission_type, &$auth_admin, &$user_id, &$group_id, &$forum_id)
+	function remove_permissions($mode, $permission_type, $auth_admin, &$user_id, &$group_id, &$forum_id)
 	{
 		global $user, $db, $cache, $auth;
 
diff --git a/phpBB/includes/acp/acp_profile.php b/phpBB/includes/acp/acp_profile.php
index d89c200a1b..49da7d84a4 100644
--- a/phpBB/includes/acp/acp_profile.php
+++ b/phpBB/includes/acp/acp_profile.php
@@ -845,7 +845,7 @@ class acp_profile
 	/**
 	* Build all Language specific options
 	*/
-	function build_language_options(&$cp, $field_type, $action = 'create')
+	function build_language_options($cp, $field_type, $action = 'create')
 	{
 		global $user, $config, $db, $request;
 
@@ -942,7 +942,7 @@ class acp_profile
 	/**
 	* Save Profile Field
 	*/
-	function save_profile_field(&$cp, $field_type, $action = 'create')
+	function save_profile_field($cp, $field_type, $action = 'create')
 	{
 		global $db, $config, $user, $phpbb_container, $phpbb_log, $request, $phpbb_dispatcher;
 
diff --git a/phpBB/includes/acp/acp_users.php b/phpBB/includes/acp/acp_users.php
index b74fe535ee..2d1eaadfae 100644
--- a/phpBB/includes/acp/acp_users.php
+++ b/phpBB/includes/acp/acp_users.php
@@ -24,9 +24,9 @@ class acp_users
 	var $u_action;
 	var $p_master;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/functions_compatibility.php b/phpBB/includes/functions_compatibility.php
index 6ae72076e7..96398775a2 100644
--- a/phpBB/includes/functions_compatibility.php
+++ b/phpBB/includes/functions_compatibility.php
@@ -362,7 +362,7 @@ function request_var($var_name, $default, $multibyte = false, $cookie = false, $
  *
  * @deprecated 3.1.0 (To be removed: 4.0.0)
  */
-function get_tables(&$db)
+function get_tables($db)
 {
 	$db_tools_factory = new \phpbb\db\tools\factory();
 	$db_tools = $db_tools_factory->get($db);
diff --git a/phpBB/includes/functions_mcp.php b/phpBB/includes/functions_mcp.php
index d91993b23f..75e24618de 100644
--- a/phpBB/includes/functions_mcp.php
+++ b/phpBB/includes/functions_mcp.php
@@ -22,12 +22,12 @@ if (!defined('IN_PHPBB'))
 /**
 * Functions used to generate additional URL paramters
 */
-function phpbb_module__url($mode, &$module_row)
+function phpbb_module__url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
 
-function phpbb_module_notes_url($mode, &$module_row)
+function phpbb_module_notes_url($mode, $module_row)
 {
 	if ($mode == 'front')
 	{
@@ -38,7 +38,7 @@ function phpbb_module_notes_url($mode, &$module_row)
 	return ($user_id) ? "&u=$user_id" : '';
 }
 
-function phpbb_module_warn_url($mode, &$module_row)
+function phpbb_module_warn_url($mode, $module_row)
 {
 	if ($mode == 'front' || $mode == 'list')
 	{
@@ -64,27 +64,27 @@ function phpbb_module_warn_url($mode, &$module_row)
 	}
 }
 
-function phpbb_module_main_url($mode, &$module_row)
+function phpbb_module_main_url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
 
-function phpbb_module_logs_url($mode, &$module_row)
+function phpbb_module_logs_url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
 
-function phpbb_module_ban_url($mode, &$module_row)
+function phpbb_module_ban_url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
 
-function phpbb_module_queue_url($mode, &$module_row)
+function phpbb_module_queue_url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
 
-function phpbb_module_reports_url($mode, &$module_row)
+function phpbb_module_reports_url($mode, $module_row)
 {
 	return phpbb_extra_url();
 }
diff --git a/phpBB/includes/mcp/mcp_logs.php b/phpBB/includes/mcp/mcp_logs.php
index 049f24b262..79f9d35ebe 100644
--- a/phpBB/includes/mcp/mcp_logs.php
+++ b/phpBB/includes/mcp/mcp_logs.php
@@ -28,9 +28,9 @@ class mcp_logs
 	var $u_action;
 	var $p_master;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_main.php b/phpBB/includes/mcp/mcp_main.php
index 196d2f995f..a4e3a74ba7 100644
--- a/phpBB/includes/mcp/mcp_main.php
+++ b/phpBB/includes/mcp/mcp_main.php
@@ -28,9 +28,9 @@ class mcp_main
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_notes.php b/phpBB/includes/mcp/mcp_notes.php
index 12b116e495..a4c2356a43 100644
--- a/phpBB/includes/mcp/mcp_notes.php
+++ b/phpBB/includes/mcp/mcp_notes.php
@@ -28,9 +28,9 @@ class mcp_notes
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_pm_reports.php b/phpBB/includes/mcp/mcp_pm_reports.php
index ba89733bfe..eecfe9cbc8 100644
--- a/phpBB/includes/mcp/mcp_pm_reports.php
+++ b/phpBB/includes/mcp/mcp_pm_reports.php
@@ -28,9 +28,9 @@ class mcp_pm_reports
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_queue.php b/phpBB/includes/mcp/mcp_queue.php
index a95c8fad44..dec583f6f4 100644
--- a/phpBB/includes/mcp/mcp_queue.php
+++ b/phpBB/includes/mcp/mcp_queue.php
@@ -28,9 +28,9 @@ class mcp_queue
 	var $p_master;
 	var $u_action;
 
-	public function __construct(&$p_master)
+	public function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	public function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_reports.php b/phpBB/includes/mcp/mcp_reports.php
index b4018184a7..4600257344 100644
--- a/phpBB/includes/mcp/mcp_reports.php
+++ b/phpBB/includes/mcp/mcp_reports.php
@@ -28,9 +28,9 @@ class mcp_reports
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/mcp/mcp_warn.php b/phpBB/includes/mcp/mcp_warn.php
index 888069ef5d..df175133fc 100644
--- a/phpBB/includes/mcp/mcp_warn.php
+++ b/phpBB/includes/mcp/mcp_warn.php
@@ -28,9 +28,9 @@ class mcp_warn
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/includes/ucp/ucp_main.php b/phpBB/includes/ucp/ucp_main.php
index ec652a5e45..5214de8c7c 100644
--- a/phpBB/includes/ucp/ucp_main.php
+++ b/phpBB/includes/ucp/ucp_main.php
@@ -28,9 +28,9 @@ class ucp_main
 	var $p_master;
 	var $u_action;
 
-	function __construct(&$p_master)
+	function __construct($p_master)
 	{
-		$this->p_master = &$p_master;
+		$this->p_master = $p_master;
 	}
 
 	function main($id, $mode)
diff --git a/phpBB/phpbb/captcha/plugins/gd.php b/phpBB/phpbb/captcha/plugins/gd.php
index 831e5bcfdf..6d3c9bb3d2 100644
--- a/phpBB/phpbb/captcha/plugins/gd.php
+++ b/phpBB/phpbb/captcha/plugins/gd.php
@@ -51,7 +51,7 @@ class gd extends captcha_abstract
 		return 'CAPTCHA_GD';
 	}
 
-	function acp_page($id, &$module)
+	function acp_page($id, $module)
 	{
 		global $user, $template, $phpbb_log, $request;
 		global $config;
diff --git a/phpBB/phpbb/captcha/plugins/gd_wave.php b/phpBB/phpbb/captcha/plugins/gd_wave.php
index bde46f8815..4ac26ed2b7 100644
--- a/phpBB/phpbb/captcha/plugins/gd_wave.php
+++ b/phpBB/phpbb/captcha/plugins/gd_wave.php
@@ -33,7 +33,7 @@ class gd_wave extends captcha_abstract
 		return '\\phpbb\\captcha\\gd_wave';
 	}
 
-	function acp_page($id, &$module)
+	function acp_page($id, $module)
 	{
 		global $user;
 
diff --git a/phpBB/phpbb/captcha/plugins/nogd.php b/phpBB/phpbb/captcha/plugins/nogd.php
index 6845e5935c..da67cd2bf4 100644
--- a/phpBB/phpbb/captcha/plugins/nogd.php
+++ b/phpBB/phpbb/captcha/plugins/nogd.php
@@ -33,7 +33,7 @@ class nogd extends captcha_abstract
 		return '\\phpbb\\captcha\\non_gd';
 	}
 
-	function acp_page($id, &$module)
+	function acp_page($id, $module)
 	{
 		global $user;
 
diff --git a/phpBB/phpbb/captcha/plugins/qa.php b/phpBB/phpbb/captcha/plugins/qa.php
index 7797212ac9..8f41434601 100644
--- a/phpBB/phpbb/captcha/plugins/qa.php
+++ b/phpBB/phpbb/captcha/plugins/qa.php
@@ -638,7 +638,7 @@ class qa
 	/**
 	*  API function - The ACP backend, this marks the end of the easy methods
 	*/
-	function acp_page($id, &$module)
+	function acp_page($id, $module)
 	{
 		global $config, $request, $phpbb_log, $template, $user;
 
@@ -776,7 +776,7 @@ class qa
 	/**
 	*  This handles the list overview
 	*/
-	function acp_question_list(&$module)
+	function acp_question_list($module)
 	{
 		global $db, $template;
 
diff --git a/phpBB/phpbb/captcha/plugins/recaptcha.php b/phpBB/phpbb/captcha/plugins/recaptcha.php
index 152709a9ea..b7c0b5f5e2 100644
--- a/phpBB/phpbb/captcha/plugins/recaptcha.php
+++ b/phpBB/phpbb/captcha/plugins/recaptcha.php
@@ -66,7 +66,7 @@ class recaptcha extends captcha_abstract
 		throw new \Exception('No generator class given.');
 	}
 
-	function acp_page($id, &$module)
+	function acp_page($id, $module)
 	{
 		global $config, $template, $user, $phpbb_log, $request;
 
diff --git a/phpBB/phpbb/files/upload.php b/phpBB/phpbb/files/upload.php
index a9bf74094d..50e15c9844 100644
--- a/phpBB/phpbb/files/upload.php
+++ b/phpBB/phpbb/files/upload.php
@@ -261,7 +261,7 @@ class upload
 	 *
 	 * @param filespec $file Instance of filespec class
 	 */
-	public function common_checks(&$file)
+	public function common_checks($file)
 	{
 		// Filesize is too big or it's 0 if it was larger than the maxsize in the upload form
 		if ($this->max_filesize && ($file->get('filesize') > $this->max_filesize || $file->get('filesize') == 0))
@@ -297,7 +297,7 @@ class upload
 	 *
 	 * @return bool True if extension is allowed, false if not
 	 */
-	public function valid_extension(&$file)
+	public function valid_extension($file)
 	{
 		return (in_array($file->get('extension'), $this->allowed_extensions)) ? true : false;
 	}
@@ -310,7 +310,7 @@ class upload
 	 * @return bool True if dimensions are valid or no constraints set, false
 	 *			if not
 	 */
-	public function valid_dimensions(&$file)
+	public function valid_dimensions($file)
 	{
 		if (!$this->max_width && !$this->max_height && !$this->min_width && !$this->min_height)
 		{
@@ -350,7 +350,7 @@ class upload
 	 *
 	 * @return bool True if content is valid, false if not
 	 */
-	public function valid_content(&$file)
+	public function valid_content($file)
 	{
 		return ($file->check_content($this->disallowed_content));
 	}
diff --git a/tests/upload/filespec_test.php b/tests/upload/filespec_test.php
index 29f6a017b2..e8b5d22205 100644
--- a/tests/upload/filespec_test.php
+++ b/tests/upload/filespec_test.php
@@ -79,7 +79,7 @@ class phpbb_filespec_test extends phpbb_test_case
 		$this->phpbb_root_path = $phpbb_root_path;
 	}
 
-	private function set_reflection_property(&$class, $property_name, $value)
+	private function set_reflection_property($class, $property_name, $value)
 	{
 		$property = new ReflectionProperty($class, $property_name);
 		$property->setAccessible(true);