I've released PHP 7 OCI8 2.1 on PECL and simultaneously made a patch release OCI8 2.0.10 which is compatible with PHP 5.2 - PHP 5.6.
To install OCI8 for PHP 7 use:
pecl install oci8
This installs OCI8 2.1 which, as I'm sure you can guess, had a lot of internal changes to make it compatible with the vastly changed internals of PHP 7.
If you want to install OCI8 for PHP 5.2, 5.3, 5.4, or 5.6 use:
pecl install oci8-2.0.10
Functionality in 2.0.10 and 2.1.0 is equivalent. They both contain the fix for bug 68298, an overflow when binding 64bit numbers.
[Update: Windows DLLs have been built.] At time of writing, Windows DLLs were not yet built on PECL. If you need them, you can grab them from the full PHP Windows bundle.