php-watcher has unmet requirements

[SlausB]

I'm trying to install php-watcher within latest composer docker with composer require seregazhuk/php-watcher command, but getting error:

Package seregazhuk/php-watcher has a PHP requirement incompatible with your PHP version, PHP extensions and Composer version

Docker container has Composer version 2.0.11 2021-02-24 14:57:23 and PHP 8.0.3 (cli) (built: Mar 6 2021 03:28:33) ( NTS ).

I'm new to PHP and not sure what composer require --ignore-platform-reqs seregazhuk/php-watcher is doing, but after that ./vendor/bin/php-watcher app.php gives:

Fatal error: Uncaught Error: Undefined constant "seregazhuk\PhpWatcher\Config\SIGINT" in /app/vendor/seregazhuk/php-watcher/src/Config/Config.php:40
Stack trace:
#0 /app/vendor/seregazhuk/php-watcher/src/Config/Builder.php(21): seregazhuk\PhpWatcher\Config\Config::fromArray(Array)
#1 /app/vendor/seregazhuk/php-watcher/src/WatcherCommand.php(73): seregazhuk\PhpWatcher\Config\Builder->fromConfigFile('')
#2 /app/vendor/seregazhuk/php-watcher/src/WatcherCommand.php(42): seregazhuk\PhpWatcher\WatcherCommand->buildConfig(Object(Symfony\Component\Console\Input\ArgvInput))
#3 /app/vendor/symfony/console/Command/Command.php(256): seregazhuk\PhpWatcher\WatcherCommand->execute(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#4 /app/vendor/symfony/console/Application.php(971): Symfony\Component\Console\Command\Command->run(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#5 /app/vendor/symfony/console/Application.php(290): Symfony\Component\Console\Application->doRunCommand(Object(seregazhuk\PhpWatcher\WatcherCommand), Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#6 /app/vendor/symfony/console/Application.php(166): Symfony\Component\Console\Application->doRun(Object(Symfony\Component\Console\Input\ArgvInput), Object(Symfony\Component\Console\Output\ConsoleOutput))
#7 /app/vendor/seregazhuk/php-watcher/php-watcher(18): Symfony\Component\Console\Application->run()

And now composer check-platform-reqs outputs:

Checking platform requirements for packages in the vendor dir
ext-curl      8.0.3                                                 success  
ext-json      8.0.3                                                 success  
ext-mbstring  8.0.3                                                 success  
ext-pcntl     n/a    seregazhuk/php-watcher requires ext-pcntl (*)  missing  
php           8.0.3  seregazhuk/php-watcher requires php (^7.2)     failed   

Is there a way I could use php-watcher in such setup?

[benpoulson]

@SlausB install using dev-master as your version.

composer require seregazhuk/php-watcher --dev dev-master