diff --git a/system/core/Common.php b/system/core/Common.php
index 03f62c09..158213c0 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -727,6 +727,9 @@ if ( ! function_exists('remove_invisible_characters'))
 
 		do
 		{
+			if ($str == null) {
+                $str = "";
+            }
 			$str = preg_replace($non_displayables, '', $str, -1, $count);
 		}
 		while ($count);
diff --git a/system/libraries/Profiler.php b/system/libraries/Profiler.php
index 5531f336..0ef908bc 100644
--- a/system/libraries/Profiler.php
+++ b/system/libraries/Profiler.php
@@ -490,10 +490,10 @@ class CI_Profiler {
 			if (is_array($val) OR is_object($val))
 			{
 				$val = print_r($val, TRUE);
-
 				$pre       = '<pre>' ;
 				$pre_close = '</pre>';
 			}
+			$val = $val == null ? "" : $val;
 
 			$output .= '<tr><td style="padding:5px;vertical-align:top;color:#900;background-color:#ddd;">'
 				.$config.'&nbsp;&nbsp;</td><td style="padding:5px;color:#000;background-color:#ddd;">'.$pre.htmlspecialchars($val, ENT_QUOTES, config_item('charset')).$pre_close."</td></tr>\n";
@@ -522,6 +522,7 @@ class CI_Profiler {
 
 		foreach ($this->CI->session->userdata() as $key => $val)
 		{
+			$val = $val == null ? "" : $val;
 			$pre       = '';
 			$pre_close = '';
 
diff --git a/system/libraries/Session/drivers/Session_files_driver.php b/system/libraries/Session/drivers/Session_files_driver.php
index 49bf5b78..af380524 100644
--- a/system/libraries/Session/drivers/Session_files_driver.php
+++ b/system/libraries/Session/drivers/Session_files_driver.php
@@ -129,7 +129,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 * @param	string	$name		Session cookie name
 	 * @return	bool
 	 */
-	public function open($save_path, $name)
+	public function open($save_path, $name): bool
 	{
 		if ( ! is_dir($save_path))
 		{
@@ -165,6 +165,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 * @param	string	$session_id	Session ID
 	 * @return	string	Serialized session data
 	 */
+	#[\ReturnTypeWillChange]
 	public function read($session_id)
 	{
 		// This might seem weird, but PHP 5.6 introduces session_reset(),
@@ -238,6 +239,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 * @param	string	$session_data	Serialized session data
 	 * @return	bool
 	 */
+	#[\ReturnTypeWillChange]
 	public function write($session_id, $session_data)
 	{
 		// If the two IDs don't match, we have a session_regenerate_id() call
@@ -295,6 +297,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 *
 	 * @return	bool
 	 */
+	#[\ReturnTypeWillChange]
 	public function close()
 	{
 		if (is_resource($this->_file_handle))
@@ -318,6 +321,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 * @param	string	$session_id	Session ID
 	 * @return	bool
 	 */
+	#[\ReturnTypeWillChange]
 	public function destroy($session_id)
 	{
 		if ($this->close() === $this->_success)
@@ -359,6 +363,7 @@ class CI_Session_files_driver extends CI_Session_driver implements SessionHandle
 	 * @param	int 	$maxlifetime	Maximum lifetime of sessions
 	 * @return	bool
 	 */
+	#[\ReturnTypeWillChange]
 	public function gc($maxlifetime)
 	{
 		if ( ! is_dir($this->_config['save_path']) OR ($directory = opendir($this->_config['save_path'])) === FALSE)