You may want to wait for a specific output of the process you started

asynchronously, for this use case you may use the method

:method:`Symfony\\Component\\Process\\Process::waitUntil`:

$process = new Process(array('/usr/bin/php', 'slow-starting-server.php'));

$process->start();

// ... do other things

$process->waitUntil(function ($type, $output) {

return $output === 'Ready. Waiting for commands...';

});

// ... do things after the process is ready

Streaming to the Standard Input of a Process