How to fix this error Package phpunit/phpunit-mock-objects is abandoned, you should avoid using it. No replacement was suggested

PHPUnit version           PHP Version          composer
   -----------------       ---------------       -------------------------
   PHPUnit 8                PHP 7.2 / 7.3         "phpunit/phpunit": "^8"
   PHPUnit 7                PHP 7.1               "phpunit/phpunit": "^7"
   PHPUnit 6                PHP 7.0               "phpunit/phpunit": "^6"
   PHPUnit 5                PHP 5.6               "phpunit/phpunit": "^5"

Note: PHP 7.1 is no longer actively supported.
See this link

composer: add --ignore-platform-reqs