No input file specified Error (not GoDaddy)

[theez1]

My store (1.7 or 1.8, not entirely sure which) was fine one day and replaced with this error message the next: "No input file specified". I have seen that it is a common problem with GoDaddy hosting, but I am not with them. I have tried all of the suggestions I found for the GoDaddy issue though but nothing is working. I have had it hosted at this location since it was created 3 years ago. My host updated PHP to 5.6.28, which seems to have triggered this. Does anyone have any idea what could be going on, or what I can try? I'm desperate. I know it's long overdue for an upgrade, but I don't want to attempt it while it's broken.

[theez1]

The update was actually PHP 5.6.16 to PHP 5.6.17.

[JLHC]

Are you sure that you are using Magento 1.7 or 1.8?

Both versions are not compatible with PHP 5.4 and above unless they are patched:-

https://magento.com/blog/magento-news/magento-now-supports-php-54

And the patch still doesn't guarantee full compatibility with PHP 5.6. 

[theez1]

It's 1.8.

After being down for 2 days and trying everything I could, the store came back today on it's own. The host claims that nothing was done on their end, so I have no idea what's going on. Gonna try to upgrade over the weekend.