Error 500 on update

Updated the core folder to 2.8.26 and reloaded my home page only to see an error 500.

Server logs reports the following:

PHP Parse error:  syntax error, unexpected '[', expecting ')' in /home/xxxx/public_html/perch/core/lib/PerchFieldTypes.class.php on line 1465

Rolled back to old version but here's current report

Perch: 2.6.6, PHP: 5.3.29, MySQL: 10.0.20-MariaDB, with PDO
Server OS: Linux, cgi-fcgi
Installed apps: content (2.6.6), assets (2.6.6), categories (2.6.6), perch_blog (4.5.2), perch_gallery (2.8.5), perch_backup (1.2)
App runtimes: <?php $apps_list = array( 'content', 'categories', 'perch_gallery', 'perch_blog', );
PERCH_LOGINPATH: /perch
PERCH_PATH: /home/xxxx/public_html/perch
PERCH_CORE: /home/xxxx/public_html/perch/core
PERCH_RESFILEPATH: /home5/xxxx/public_html/files
Image manipulation: GD Imagick
PHP limits: Max upload 2M, Max POST 8M, Memory: 128M, Total max file upload: 2M
Resource folder writeable: Yes
REQUEST_URI: /perch/core/settings/diagnostics/
SCRIPT_NAME: /perch/core/settings/diagnostics/index.php

Any suggestions?