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;
    }