Do not use mb_* string functions, they are not needed.

Author: drupol

src/Exporter/Image.php

@@ -34,7 +34,7 @@ final class Image implements ExporterInterface
      */
     public function __construct()
     {
-        if (0 === mb_stripos(PHP_OS, 'WIN')) {
+        if (0 === stripos(PHP_OS, 'WIN')) {
             $this->executable = 'dot.exe';
         }
     }

src/Importer/Text.php

@@ -51,16 +51,16 @@ private function createNode(string $label): AttributeNodeInterface
     private function parse(string $subject): array
     {
         $result = [
-            'value' => mb_substr($subject, 1, mb_strpos($subject, '[', 1) - 1),
+            'value' => substr($subject, 1, strpos($subject, '[', 1) - 1),
             'children' => [],
         ];
 
-        if (false === $nextBracket = mb_strpos($subject, '[', 1)) {
+        if (false === $nextBracket = strpos($subject, '[', 1)) {
             return $result;
         }
 
         // Todo: Improve the regex.
-        preg_match_all('#[^\[\]]+|\[(?<nested>(?R)*)]#', mb_substr($subject, $nextBracket, -1), $matches);
+        preg_match_all('#[^\[\]]+|\[(?<nested>(?R)*)]#', substr($subject, $nextBracket, -1), $matches);
 
         $result['children'] = array_map(
             static function (string $match): string {

src/Node/TrieNode.php

@@ -23,10 +23,10 @@ public function add(NodeInterface ...$nodes): NodeInterface
 
             $hash = hash('sha256', $node->getKey() . $data);
 
-            $node = new self($hash, mb_substr($data, 0, 1));
+            $node = new self($hash, substr($data, 0, 1));
             $parent = $this->append($node);
 
-            $dataWithoutFirstLetter = mb_substr($data, 1);
+            $dataWithoutFirstLetter = substr($data, 1);
 
             if ('' < $dataWithoutFirstLetter) {
                 $parent->add(new self($hash, $dataWithoutFirstLetter));