code: public function configure(array $configuration = null)
      {
          parent::configure($configuration);
  
          $uniqueConfiguredExclude = array_unique($this->configuration['exclude']);
  
          // Case sensitive constants handling
          $constantsToEscape = array_values($this->configuration['include']);
          if (true === $this->configuration['fix_built_in']) {
              $getDefinedConstants = get_defined_constants(true);
              unset($getDefinedConstants['user']);
              foreach ($getDefinedConstants as $constants) {
                  $constantsToEscape = array_merge($constantsToEscape, array_keys($constants));
              }
          }
          $constantsToEscape = array_diff(
              array_unique($constantsToEscape),
              $uniqueConfiguredExclude
          );
  
          // Case insensitive constants handling
          static $caseInsensitiveConstants = ['null', 'false', 'true'];
          $caseInsensitiveConstantsToEscape = [];
          foreach ($constantsToEscape as $constantIndex => $constant) {
              $loweredConstant = strtolower($constant);
              if (\in_array($loweredConstant, $caseInsensitiveConstants, true)) {
                  $caseInsensitiveConstantsToEscape[] = $loweredConstant;
                  unset($constantsToEscape[$constantIndex]);
              }
          }
  
          $caseInsensitiveConstantsToEscape = array_diff(
              array_unique($caseInsensitiveConstantsToEscape),
              array_map(function ($function) { return strtolower($function); }, $uniqueConfiguredExclude)
          );
  
          // Store the cache
          $this->constantsToEscape = array_fill_keys($constantsToEscape, true);
          ksort($this->constantsToEscape);
  
          $this->caseInsensitiveConstantsToEscape = array_fill_keys($caseInsensitiveConstantsToEscape, true);
          ksort($this->caseInsensitiveConstantsToEscape);
      }
docs: {@inheritdoc}