Fix a bug where the Redis adapter returns an int for hasItem()

[MidnightDesign]

Version 4 of the Redis extension returns an integer instead of a boolean when exists() is called. See https://github.com/phpredis/phpredis/blob/develop/README.markdown#exists

[MidnightDesign]

Can anyone tell me what's wrong with the build?

[michalbundyra]

@MidnightDesign See #141. I've tried to fix it, but I haven't found yet any working solution for all supported PHP versions...

[MidnightDesign]

@webimpress Oh, okay. Thank you. So I'm guessing no PRs can be accepted until that issue is resolved..?

[michalbundyra]

I'm not a maintainer of that repository so I can't tell you. I know there is a plan to work on it soon, so hopefully this PR will be accepted soon. Just be patient :)

[froschdesign]

@MidnightDesign Can you help with the configuration of the cache adapters, so the tests will run on Travis? That would be great!

[MidnightDesign]

@froschdesign I can and will certainly try. I'm just nor sure I'm proficient enough with that stuff.

[michalbundyra]

@froschdesign @MidnightDesign I think I've done a lot to fix these adapters in #141 and there we have support for PHP 7.1 and 7.2 + dropped HHVM. When we start fixing it here it will create more conflicts or duplicate what I did in #141. We need these adapters working for PHP 5.6-7.2 ... I would suggest to try fix them rather on #141 than here.

[MidnightDesign]

@webimpress Yeah, of course I'd fix them/help you in #141. : )

[froschdesign]

@MidnightDesign @webimpress Sorry, I mean #141! (I added also label there)

[weierophinney]

I've verified the fix locally, running against a local redis server.

[weierophinney]

Thanks, @MidnightDesign!