It's important to note here that PHP is converting to an integer, while JS is converting to a double. Integers don't have NaN as a concept. JS doesn't have integers, but if it did it would probably make the same kind of mistake. (This is a guess of course, but a reasonable one given the other insane conversions it does.)
`parseFloat("foo") == parseFloat("foo")` and `parseInt("foo") == parseInt("foo")` in Javascript evaluate to false which is the sane thing to do. `NaN != NaN` is part of the IEEE 754 floating point standard, which predates every single one of the languages you mentioned.
We're all competing in the olympics of suffering, so none of us should be promoting this shit :)