PHP Parse error: syntax error, unexpected '?' on line 143

[enrutador]

Hi very nice work ¡¡¡¡ I have a problem when execute the Php Script :

root@icinga2 claymore-ethereum-log-genereator]# /usr/bin/php ./eth_log_gen.php

PHP Parse error:  syntax error, unexpected '?' in /usr/local/src/claymore-ethereum-log-genereator/eth_log_gen.php on line 143

My version of PHP:

[root@icinga2 claymore-ethereum-log-genereator]# php -v
PHP 5.6.40-0+deb8u2 (cli) (built: Mar 30 2019 20:26:13) 
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies
    with Zend OPcache v7.0.6-dev, Copyright (c) 1999-2016, by Zend Technologies

The error is for the version of Php ? A lot of thanks