Laravel: Cannot use helper inside php shorthand array

PHP version 5.6. Code:

protected $siteServices = [
        1 => [
            'title' =>  'Consulting',
            'key'       =>  'service',
            'description'   =>  '',
            'file'  =>  asset('assets/img/sample/image1.jpg'), // throws error on this line
        ],
];

Error: PHP Parse error: syntax error, unexpected '(', expecting ']'

What the hell?

via Chebli Mohamed