HTTP ERROR 500 with doctrine

Today in the morning I find an http500 error, when I look at my server log I find two errors repeatedly:
[Wed Aug 08 14: 22: 40.713618 2018] [: error] [pid 3987] [client] PHP Fatal error: 'Throwable' interface not found in / home / domains / public_html / vendor / doctrine / dbal /lib/Doctrine/DBAL/Driver/DriverException.php on line 33
[Wed Aug 08 14: 22: 40.717053 2018] [: error] [pid 3987] [client] PHP Parse error: syntax error, unexpected ':', expecting ';' or '{' in /home/domains/public_html/vendor/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php on line 39

I have searched for information about it and it seems that it has to do with the PHP version.
Currently we have version 5.6.23 PDO extension is also installed.
It has not changed that we know anything from yesterday to today.
I have restored the two files in question in case they had a problem, but without success.
The Elgg version is 2.3.4
I do not use composer for not having access to the terminal mode.

I do not know where to go, I hope someone can put me on the right track with this error.

Thanks in advance