Can't access Admin version 1.6.1.24 with PHP 7.1

[Bao NGUYEN]

I use wamp Server with PHP 7.1.33 to install prestashop version 1.6.1.24. It works fine frontpage without error but I try to connect to the administrator,it doesn't work ERR_CONNECTION_RESET (there is nothing in php_error.log)

switch php version 7.0.33 it's works well i can enter the backoffice.

try to debug why it doesn't work, i find the reason: when it loads file translations\fr\admin.php,  the global variable $_LANGADM is too big i put comment between line 1700 and end of file. the backoffice works well. there is not memory problem i think , in my configuration php.ini both versions i do max_input_vars = 10000 and memory_limit = 1G

there is only difference between php 7.0.33 session.hash_function = 0 vs 7.1 session.sid_length = 26

My server production is php 7.1 i can't rollback 7.0 my theme developed for version 1.6 I cannot update 1.7
how can i install prestashop 1.6.1.24 correctly?