Need to switch from PHP 5.6 to 7.1 without getting errors

I’m switching my websites to PHP 7.1 (they are currently on PHP5.6), as my host recommended the switch for safety reasons. But after doing the switch to 7.1, my website doesn’t work anymore.

I just get the error message:

“Parse error: syntax error, unexpected ‘new’ (T_NEW) in /home/clients/f6723f7063f4bf7f5d5317407a4af156/web/ on line 903”

After getting this error I reverted back to PHP 5.6 and now it’s working again.

So question is, how can I upgrade to PHP 7.1 without having that problem?