Parse error: syntax error, unexpected ‘.’, expecting ‘&’ or variable (T_VARIABLE)

How can I fix the HTTP ERROR 500:

Parse error: syntax error, unexpected '.', expecting '&' or variable (T_VARIABLE) in /../framework/src/Illuminate/Foundation/helpers.php on line XXX

Solution: 

Laravel 5.5 and higher requires PHP 7.0.0 or greater.

And please make sure you have these components on your server before install the script:

PHP 7.0.0 or greater (with PHP exec function, etc.)
OpenSSL PHP Extension
PDO PHP Extension
Mbstring PHP Extension
Tokenizer PHP Extension
XML PHP Extension
GD or Imagick
PHP Fileinfo extension
PHP Zip Archive
Rewrite Module (Apache or Nginx)

 To check the PHP version installed on your server, create a php file (ex: /phpinfo.php) on your server with the content below:

<?php
phpinfo();