Homestead installation is complete, projects cloned by git cannot run composer install and php artisan commands

running composer install reports an error as follows

Loading composer repositories with package information
Installing dependencies (including require-dev) from lock file
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - This package requires php ^7.1.3 but your PHP version (7.0.1) does not satisfy that requirement.
  Problem 2
    - Installation request for chillerlan/php-qrcode 2.0.6 -> satisfiable by chillerlan/php-qrcode[2.0.6].
    - chillerlan/php-qrcode 2.0.6 requires php >=7.0.3 -> your PHP version (7.0.1) does not satisfy that requirement.
  Problem 3
    - Installation request for chillerlan/php-traits 1.1.13 -> satisfiable by chillerlan/php-traits[1.1.13].
    - chillerlan/php-traits 1.1.13 requires php >=7.0.3 -> your PHP version (7.0.1) does not satisfy that requirement.
  Problem 4
    - Installation request for laravel/framework v5.7.5 -> satisfiable by laravel/framework[v5.7.5].
    - laravel/framework v5.7.5 requires php ^7.1.3 -> your PHP version (7.0.1) does not satisfy that requirement.
  Problem 5
    - Installation request for laravel/horizon v1.4.0 -> satisfiable by laravel/horizon[v1.4.0].
    - laravel/horizon v1.4.0 requires ext-pcntl * -> the requested PHP extension pcntl is missing from your system.
  Problem 6
    - Installation request for symfony/cache v4.1.4 -> satisfiable by symfony/cache[v4.1.4].
    - symfony/cache v4.1.4 requires php ^7.1.3 -> your PHP version (7.0.1) does not satisfy that requirement.
  Problem 7
    - doctrine/inflector v1.3.0 requires php ^7.1 -> your PHP version (7.0.1) does not satisfy that requirement.
    - doctrine/inflector v1.3.0 requires php ^7.1 -> your PHP version (7.0.1) does not satisfy that requirement.
    - Installation request for doctrine/inflector v1.3.0 -> satisfiable by doctrine/inflector[v1.3.0].

  To enable extensions, verify that they are enabled in your .ini files:
    - D:\PHPWAMP_IN2\phpwamp\server\php-7.0.1\php.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

running php artisan make:controller TestController reports an error as follows

PHP Parse error:  syntax error, unexpected "?", expecting variable (T_VARIABLE) in D
:\code\tiyu\vendor\symfony\console\Output\Output.php on line 40

Parse error: syntax error, unexpected "?", expecting variable (T_VARIABLE) in D:\cod
e\tiyu\vendor\symfony\console\Output\Output.php on line 40

then try to delete the question mark with the error as follows

PHP Fatal error:  Uncaught Error: Call to undefined function Symfony\Component\Console\Output\is_iterable() in D:\code\tiyu\vendor\symfony\console\Output\Output.php:140
Stack trace:
-sharp0 D:\code\tiyu\vendor\symfony\console\Output\Output.php(132): Symfony\Component\Console\Output\Output->write("", true, 16)
-sharp1 D:\code\tiyu\vendor\symfony\console\Application.php(741): Symfony\Component\Console\Output\Output->writeln("", 16)
-sharp2 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation\Exceptions\Handler.php(469): Symfony\Component\Console\Application->renderException(Object(Symfony\Component\Debug\Exception\Fatal
ThrowableError), Object(Symfony\Component\Console\Output\ConsoleOutput))
-sharp3 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation\Bootstrap\HandleExceptions.php(101): Illuminate\Foundation\Exceptions\Handler->renderForConsole(Object(Symfony\Component\Console\O
utput\ConsoleOutput), Object(Symfony\Component\Debug\Exception\FatalThrowableError))
-sharp4 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation in D:\code\tiyu\vendor\symfony\console\Output\Output.php on line 140
PHP Fatal error:  Uncaught Error: Call to undefined function Symfony\Component\Console\Output\is_iterable() in D:\code\tiyu\vendor\symfony\console\Output\Output.php:140
Stack trace:
-sharp0 D:\code\tiyu\vendor\symfony\console\Output\Output.php(132): Symfony\Component\Console\Output\Output->write("", true, 16)
-sharp1 D:\code\tiyu\vendor\symfony\console\Application.php(741): Symfony\Component\Console\Output\Output->writeln("", 16)
-sharp2 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation\Exceptions\Handler.php(469): Symfony\Component\Console\Application->renderException(Object(Symfony\Component\Debug\Exception\Fatal
ErrorException), Object(Symfony\Component\Console\Output\ConsoleOutput))
-sharp3 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation\Bootstrap\HandleExceptions.php(101): Illuminate\Foundation\Exceptions\Handler->renderForConsole(Object(Symfony\Component\Console\O
utput\ConsoleOutput), Object(Symfony\Component\Debug\Exception\FatalErrorException))
-sharp4 D:\code\tiyu\vendor\laravel\framework\src\Illuminate\Foundation in D:\code\tiyu\vendor\symfony\console\Output\Output.php on line 140