@l4w2game : Welcome to the wonderful world of "I don't control my own server". There's likely to be a reasonable period of overlap, since PHP 7 breaks a lot of PHP 5.x code (the deprecations have become removals, new things are deprecated, and some stuff that
should have been tossed out years ago but was simply overlooked is being removed without deprecating first) and PHP 5.5 can't run new PHP 7 code. But since PHP 7 can do a little more than twice as much (on average) with the same resources and is safer, I wouldn't expect support for 5.5 to stick around forever.
That, unfortunately, means that using bespoke code or anything that isn't being actively maintained (and with enough momentum to make it unlikely that development will cease in the mid-term) is kind of risky on shared hosting. When something popular dies, there's usually a host of migration utilities to move to something else (or a fork of the project so you can update rather than migrate if it's open source and has a passionate community), but with a smaller projects or bespoke code, you don't get a lot of choices. You can run the existing code on a server you control (VPS, dedicated, or co-located); you can take control of updating the software (if the original license permits it) for your own use (or fork it if you can stand the headaches of project maintenance); or you can take control of data migration.
As much as I hate the market-leading PHP packages — and I really, truly do hate them — I have to say that they're at least a safe choice to make. When the ecosystem changes, the software changes with it. And if something as big as WordPress, phpBB or Joomla ever dies, you can pretty much be sure that every single competitor will have a one-click migration available before the corpse has cooled.