I'm guessing this is Magento 2 autoload (although you tagged both 1.9 and 2 and 2.1, so it's a guess). The newer versions of PHP allow arrays to be defined with a "shorthand" syntax of just square brackes:
. On the last line of
app/autoload.php the bootstrapper populates the autoload stuff and an empty array is the second parameter:
This new syntax was introduced in PHP 5.4
As of PHP 5.4 you can also use the short array syntax, which replaces array() with .
I would check the version of PHP being utilized by your server. If it's 5.3, you will need to upgrade it.