installing aws php sdk - unexpected variables

I'm trying to use the AWS php sdk, and having some issues getting set up. I'm getting this error when I run my php script that requires the autoloader:

Parse error: syntax error, unexpected '$value' (T_VARIABLE) in /[directory path]/Aws/functions.php on line 36

I looked in that document, and line 36 is the one that begins with if ($pred($value)).

function filter($iterable, callable $pred){
    foreach ($iterable as $value) {
        if ($pred($value)) {
            yield $value;
        }
    }
}

Not really sure how to work around this, so any tips would be greatly appreciated. Things I've tried: installing with composer. installing with .zip.

Followed these steps: http://ift.tt/1yroVgj