Line 1576 in functions.php is:
if (intval($profilefield_value) & (2**$key))
I am not sure whether the double ** is a typo or not. I think you should open a support ticket at vbulletin.com
If they say it is a typo then delete the extra * and it should work.
I have not upgraded from a previous version to vB 4.2.5, but I run a new installation of vB 4.2.5 on my forum and it works fine without any issues.
When I changed php version from 5.4 to 7 or 7.1 It gives this is en error
Unexpected Text:
<?xml version="1.0" encoding="windows-1252"?>
<?xml version="1.0" encoding="windows-1252"?>
<errors>
<error><![CDATA[<p>Database Error</p>
Invalid SQL:
SELECT bt.userid, bt.dateline, blogtextid, ipaddress, firstblogtextid
FROM blog_text bt
JOIN blog bl USING (blogid)
LEFT JOIN ipdata ip ON (
bt.ipaddress = ip.ipid AND bt.blogtextid = ip.contentid
AND bt.userid = ip.userid AND ip.contenttypeid IN (, )
)
WHERE ipid IS NULL;
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' )
)
WHERE ipid IS NULL' at line 6]]></error>
<error_html><![CDATA[<p>Database error in vBulletin 4.2.5</p>
<p>Invalid SQL:
SELECT bt.userid, bt.dateline, blogtextid, ipaddress, firstblogtextid
FROM blog_text bt
JOIN blog bl USING (blogid)
LEFT JOIN ipdata ip ON (
bt.ipaddress = ip.ipid AND bt.blogtextid = ip.contentid
AND bt.userid = ip.userid AND ip.contenttypeid IN (, )
)
WHERE ipid IS NULL;<p>
<p>
<strong>MySQL Error</strong> : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' )
)
WHERE ipid IS NULL' at line 6<br />
<strong>Error Number</strong> : 1064<br />
<strong>Request Date</strong> : Sunday, January 13th 2019 @ 12:30:41 PM<br />
<strong>Error Date</strong> : Sunday, January 13th 2019 @ 12:30:42 PM<br />
<strong>Script</strong> : http://www.defineyolu.com/install/upgrade.php<br />
<strong>Referrer</strong> : https://www.defineyolu.com/install/upgrade.php<br />
<strong>Classname</strong> : vB_Database_MySQLi<br />
<strong>MySQL Version</strong> : 5.6.41-84.1<br />
</p>]]></error_html>
</errors>