PHP will began with <?php tag. Do not include it to your VM. BTW, editor cannot highlight code without that tag.
We made some updates to PHP (well, we made two new "languages"):
https://repl.it/languages/php_cli - New and improved PHP language for command line interface shenanigans. Supports multiple files and syntax highlighting.
https://repl.it/languages/php7 - PHP Web servers! Just like other hosted repls, this allows you to write websites using PHP.