Steps to reproduce the issue

Enable Smart Search component and create a menu item to it.

Expected result

Smart search page

Actual result

Parse error: syntax error, unexpected '[', expecting ')' in components/com_finder/helpers/html/filter.php on line 112

System information (as much as possible)

PHP 5.3.29

Additional comments

Can be fixed by change line 112 in components/com_finder/helpers/html/filter.php
From

$html .= JHtml::_('bootstrap.startAccordion', 'accordion', array('parent' => true, 'active' => 'accordion-' . array_keys($branches)[0]));

To

$branch_keys = array_keys($branches);
$html .= JHtml::_('bootstrap.startAccordion', 'accordion', array('parent' => true, 'active' => 'accordion-' . $branch_keys[0]));