Symfony Command that read file from file name or STDIN

MyCommand.php

<?php

namespace AmceBundle\Command;

class MyCommand
{
    // ...
    
    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $filename = $input->getArgument('filename');

        if ($filename = $input->getArgument('filename')) {
            $contents = file_get_contents($filename);
        } else if (0 === ftell(STDIN)) {
            $contents = '';
            while (!feof(STDIN)) {
                $contents .= fread(STDIN, 1024);
            }
        } else {
            throw new \RuntimeException("Please provide a filename or pipe template content to STDIN.");
        }
        
        // Do whatever you want with `$contents`
    }
}