Site hacked but couldn’t make any sense

[ Moved to Fixing WordPress ]

Hi fellows, my client’s site was hacked few days ago
I saw results on google and go wp-admin panel to see what’s wrong with his site but couldn’t find anything even not a single plugin than i checked his cpanel too what’s wrong with web?
In hacking results, search engine was showing some creepy title, search engine screen shoot .

In cpanel i found error log, which was showing something like this:

[16-Mar-2017 01:20:47 UTC] PHP Warning:  file_get_contents(<strong>https://snacksshop.top/sunshine/0310jc1062/pages.php?/30961653w6t2_0559125361/td41wm00ta83di1.fires</strong>|mysite.com): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
 in /home/user1111/public_html/mysite.com/index.php on line 36

[26-Mar-2017 07:39:53 UTC] PHP Warning:  file_get_contents(https://snacksshop.top/sunshine/0310jc1062/pages.php?/30961655v2f6_58911737981/yv86qf31pt96kp1.fires|example.com): failed to open stream: HTTP request failed! HTTP/1.1 500 Internal Server Error
 in /home/user11111111/public_html/example.com/index.php on line 36

The web which is visible is linked to hacker’s sources. In google search results can be see japanese title and description, when i copy the same title and search with those titles there was lot of other site which was effect with hacking flow.
Can any one explain how this can be possible to hack like this?
My error log file is 28mb ^_^ but all lines are same.. is this was a major attack on wordpress sites?