Error instal phpunit Cannot use PHPUnit\Framework\MockObject\Stub as Stub

i have problem when installing phpunit.

I'have dl phpunit-6.5.5.phar, rename it phpunit.phar and create the phpunit.cmd.

My probleme is when i type "phpunit --version" .

An error returned to me : " Fatal error: Cannot use PHPUnit\Framework\MockObject\Stub as Stub because the name is already in use in phar://C:/bin/phpunit-6.5.5.phar/phpunit-mock-objects/Builder/InvocationMocker.php on line 16 "

if you have already encountered this error, thank you for your help :)