PHP7 + Synth issue

[Matt Smith]

Hi guys, I'm using the ports-mgmt/synth package builder to build my 
packages.  I just tried to build all of the packages for PHP7 from the 
new ports and came across an issue. If I set php=7.0 in DEFAULT_VERSIONS 
in the LiveSystem-make.conf (make.conf) then Synth bails out and refuses 
to build the repository. It does this:

Scanning entire ports tree.
 progress: 5.93%
 culprit: comms/atslog
 Scan aborted because dependency could not be located.
 databases/php70-mysql (required dependency of comms/atslog) does not 
 exist.

It looks like it scans the port tree, come across a port that has 
USE_PHP=mysql in it and then bails because the port 
databases/php70-mysql does not exist. Obviously because mysql was 
removed from PHP7 in favour of mysqli.

Is this a problem with the ports infrastructure or should I just not 
declare php=7.0 in the DEFAULT_VERSIONS? If I do this then it builds 
fine, but I guess that might cause other issues elsewhere.

-- 
Matt