hello to all

i need some assistant.
i performed a manual upgrade from version 2.71 to 3.14.
it seems ended ok ,
but when i try to lofin to admin page i get php error:

Fatal error: Can't use method return value in write context in /var/www/html/limesurvey/application/models/TemplateManifest.php on line 558

Hi, How did you solve this? I am getting the same error when tried to manually upgrade from version 2.63 to 3.15

what is your PHP version?

Hi, we are using PHP version 5.6.32
PS: We are planning to upgrade to PHP 7.2 next month.