code: private function findHeaderCommentInsertionIndex(Tokens $tokens)
      {
          if ('after_open' === $this->configuration['location']) {
              return 1;
          }
  
          $index = $tokens->getNextMeaningfulToken(0);
          if (null === $index) {
              // file without meaningful tokens but an open tag, comment should always be placed directly after the open tag
              return 1;
          }
  
          if (!$tokens[$index]->isGivenKind(T_DECLARE)) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($index);
          if (null === $next || !$tokens[$next]->equals('(')) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($next);
          if (null === $next || !$tokens[$next]->equals([T_STRING, 'strict_types'], false)) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($next);
          if (null === $next || !$tokens[$next]->equals('=')) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($next);
          if (null === $next || !$tokens[$next]->isGivenKind(T_LNUMBER)) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($next);
          if (null === $next || !$tokens[$next]->equals(')')) {
              return 1;
          }
  
          $next = $tokens->getNextMeaningfulToken($next);
          if (null === $next || !$tokens[$next]->equals(';')) { // don't insert after close tag
              return 1;
          }
  
          return $next + 1;
      }
docs: Find the index where the header comment must be inserted.
  
  @param Tokens $tokens
  
  @return int