For a long time, PhpStorm has only supported JRE 1.6 out of the box, requiring installing the out-of-date Apple version to run. One prominent issue with newer JRE versions on OSX was that a discrete GPU would always be enabled, sucking battery life unnecessarily. There didn't seem to be any concrete, critical issues for some time, but the scary warning about using newer JREs remained.
PhpStorm specified this restriction in the application's Info.plist file with this value:
In PhpStorm 10, a seemingly trivial change has fixed the discrete graphics card problem, and it has been updated so that it should use newer versions:
However, when I started PhpStorm 10 it continued to use JRE 1.6, even though I have JRE 1.8 available.
The problem turned out to be that ~/Library/Preferences/WebIde100/idea.properties had been migrated from my previous version of PhpStorm, and it (probably by my own doing) contained a further restriction on the Java version for PhpStorm to use, that overrides the Info.plist value:
Removing that declaration allowed PhpStorm to start with Oracle JRE 1.8 as expected.