PHP7 install: libcurl3 and libwebp5 are depends, but not installable

Question

I'm trying to run the following command in order to set up a web server on my Raspberry Pi 3 running Raspbian.

sudo apt-get install nginx php7.0-fpm php7.0-curl php7.0-xml php7.0-json php7.0-zip php7.0-mb php7.0-mysql php7.0-mcrypt php7.0-gd

When I run this, at the end of the output, I get the message:

The following packages have unmet dependedencies:
  php7.0-curl : Depends: libcurl3 (>= 7.18.0) but it is not installable
  php7.0-gd : Depends: libwebp5 but it is not installable

I've done a lot of searching and found that I do, in fact, have libcurl4 installed but I'm not able to figure much out. I've done sudo apt-get update -y && sudo apt-get upgrade -y before trying to install.

Any help is much appreciated; I've tried a fair amount to figure this out on my own and have done a ton of searching (hopefully enough to where somebody doesn't link me a thread that answers my exact question), so I'm hoping for a little bit of help here.

Thanks in advance.