Hello,
It seems a Safari (webkit) issue:
http://stackoverflow.com/questions/14680807/how-to-fix-webkit-fake-url-mean
https://github.com/jejacks0n/mercury/issues/179
https://bugs.webkit.org/show_bug.cgi?id=49141
That it's not sending a correct path for images.
About PHP7, it's officially supported since phpdocx 5.1.
Regards.