diff --git a/boards/bbpress.php b/boards/bbpress.php
index 8fc9de3..56cbcdf 100644
--- a/boards/bbpress.php
+++ b/boards/bbpress.php
@@ -97,7 +97,7 @@ class BBPRESS_Converter extends Converter
 	 * @param string $gids A serialized list of original roles
 	 * @return string group id(s)
 	 */
-	function get_group_id($gids)
+	function get_group_id($gids, $remove=array())
 	{
 		// bbPress saves roles as ["name" => true]
 		$roles = array_keys(unserialize($gids));
diff --git a/boards/ipb3/polls.php b/boards/ipb3/polls.php
index 633d8f7..7c81e39 100644
--- a/boards/ipb3/polls.php
+++ b/boards/ipb3/polls.php
@@ -44,7 +44,7 @@ function convert_data($data)
 		$insert_data['import_tid'] = $data['tid'];
 		$insert_data['import_pid'] = $data['pid'];
 		$insert_data['tid'] = $this->get_import->tid($data['tid']);
-		$choices = unserialize(utf8_decode($data['choices']));
+		$choices = unserialize(mb_convert_encoding($data['choices'], 'ISO-8859-1', 'UTF-8'));
 		$choices = $choices[1];
 
 		$seperator = '';
diff --git a/boards/vbulletin3/privatemessages.php b/boards/vbulletin3/privatemessages.php
index fad704c..ff897f6 100644
--- a/boards/vbulletin3/privatemessages.php
+++ b/boards/vbulletin3/privatemessages.php
@@ -60,8 +60,10 @@ function convert_data($data)
 		// However afterwards we need to properly encode all elements again, otherwise we'd get other issues again
 		if(!is_array($touserarray))
 		{
-			$touserarray = unserialize(utf8_decode($data['touserarray']));
-			array_walk_recursive($touserarray, create_function('&$value, $key', '$value = utf8_encode($value);'));
+			$touserarray = unserialize(mb_convert_encoding($data['touserarray'], 'ISO-8859-1', 'UTF-8'));
+			array_walk_recursive($touserarray, function (&$value, &$key) {
+				$value = mb_convert_encoding($value, 'UTF-8', 'ISO-8859-1');
+			});
 		}
 
 		// This is the original check in vB
diff --git a/boards/vbulletin4/privatemessages.php b/boards/vbulletin4/privatemessages.php
index c48e90b..2ff214d 100644
--- a/boards/vbulletin4/privatemessages.php
+++ b/boards/vbulletin4/privatemessages.php
@@ -60,8 +60,10 @@ function convert_data($data)
 		// However afterwards we need to properly encode all elements again, otherwise we'd get other issues again
 		if(!is_array($touserarray))
 		{
-			$touserarray = unserialize(utf8_decode($data['touserarray']));
-			array_walk_recursive($touserarray, create_function('&$value, $key', '$value = utf8_encode($value);'));
+			$touserarray = unserialize(mb_convert_encoding($data['touserarray'], 'ISO-8859-1', 'UTF-8'));
+			array_walk_recursive($touserarray, function (&$value, &$key) {
+				$value = mb_convert_encoding($value, 'UTF-8', 'ISO-8859-1');
+			});
 		}
 
 		// This is the original check in vB
diff --git a/boards/vbulletin5/privatemessages.php b/boards/vbulletin5/privatemessages.php
index 6757aa5..5a22ddb 100644
--- a/boards/vbulletin5/privatemessages.php
+++ b/boards/vbulletin5/privatemessages.php
@@ -60,8 +60,10 @@ function convert_data($data)
 		// However afterwards we need to properly encode all elements again, otherwise we'd get other issues again
 		if(!is_array($touserarray))
 		{
-			$touserarray = unserialize(utf8_decode($data['touserarray']));
-			array_walk_recursive($touserarray, create_function('&$value, $key', '$value = utf8_encode($value);'));
+			$touserarray = unserialize(mb_convert_encoding($data['touserarray'], 'ISO-8859-1', 'UTF-8'));
+			array_walk_recursive($touserarray, function (&$value, &$key) {
+				$value = mb_convert_encoding($value, 'UTF-8', 'ISO-8859-1');
+			});
 		}
 
 		// This is the original check in vB
diff --git a/loginconvert.php b/loginconvert.php
index aa58bdb..40994e8 100644
--- a/loginconvert.php
+++ b/loginconvert.php
@@ -160,9 +160,12 @@ function loginconvert_convert(&$login)
 		$check = $function($login->data['password'], $user);
 
 		// If the password was wrong, an utf8 password and we want to check utf8 passwords we call the function again
-		if(!$check && in_array($login_type, $utf8_recheck) && utf8_decode($login->data['password']) != $login->data['password'])
+		if(!$check && in_array($login_type, $utf8_recheck) && mb_convert_encoding(
+			$login->data['password'],
+			'ISO-8859-1',
+			'UTF-8') !== $login->data['password'])
 		{
-			$check = $function(utf8_decode($login->data['password']), $user);
+			$check = $function(mb_convert_encoding($login->data['password'], 'ISO-8859-1', 'UTF-8'), $user);
 		}
 
 		if(!$check)
@@ -331,6 +334,11 @@ function check_punbb($password, $user)
 	{
 		return true;
 	}
+	elseif(function_exists('hash') && $is_sha1 && (hash('sha1', $password) === $user['passwordconvert'] || hash('sha1', $user['passwordconvertsalt'].hash('sha1', $password)) === $user['passwordconvert']))
+	{
+		return true;
+	}
+    // mhash() is deprecated as of PHP8.1
 	elseif(function_exists('mhash') && $is_sha1 && (bin2hex(mhash(MHASH_SHA1, $password)) == $user['passwordconvert'] || bin2hex(mhash(MHASH_SHA1, $user['passwordconvertsalt'].bin2hex(mhash(MHASH_SHA1, $password)))) == $user['passwordconvert']))
 	{
 		return true;
diff --git a/resources/functions.php b/resources/functions.php
index 6a3a83c..a7b805e 100644
--- a/resources/functions.php
+++ b/resources/functions.php
@@ -459,12 +459,12 @@ function encode_to_utf8($text, $old_table_name, $new_table_name)
     {
         if(!function_exists('iconv'))
         {
-            if(fetch_iconv_encoding($import_session['table_charset_old'][$old_table_name]) != 'iso-8859-1' || !function_exists("utf8_encode"))
+            if(fetch_iconv_encoding($import_session['table_charset_old'][$old_table_name]) != 'iso-8859-1' || !function_exists("mb_convert_encoding"))
             {
                 return $text;
             }
 
-			return utf8_encode($text);
+			return mb_convert_encoding($text, 'UTF-8', 'ISO-8859-1');
         }
 
 		$converted_str = iconv(fetch_iconv_encoding($import_session['table_charset_old'][$old_table_name]), fetch_iconv_encoding($import_session['table_charset_new'][$new_table_name]).'//TRANSLIT', $text);
@@ -781,8 +781,12 @@ function htmlspecialchars_decode($text)
 function utf8_unhtmlentities($string)
 {
 	// Replace numeric entities
-	$string = preg_replace_callback('~&#x([0-9a-f]+);~i', create_function('$matches', 'return unichr(hexdec($matches[1]));'), $string);
-	$string = preg_replace_callback('~&#([0-9]+);~', create_function('$matches', 'return unichr($matches[1]);'), $string);
+	$string = preg_replace_callback('~&#x([0-9a-f]+);~i', function($matches) {
+		return unichr(hexdec($matches[1]));
+	}, $string);
+	$string = preg_replace_callback('~&#([0-9]+);~', function($matches) {
+		return unichr($matches[1]);
+	}, $string);
 
 	// Replace literal entities
 	$trans_tbl = get_html_translation_table(HTML_ENTITIES);