A good point to be made about "PHP to Java" conversions is that someone might want, instead of converting to Java, to convert to Kotlin. While we don't have an explicit "PHP to Kotlin" converter, it is perfectly feasible to convert "PHP -> Java -> Kotlin" by using the Runtime Converter in coordination with JetBrains Java to Kotlin converter.
Just as with Java, PHP-> Kotlin converted code will need manual work to fully take advantage of native language features.
Kotlin is an excellent language, fully compatible and convertable from Java, which offers advanced null-safety and type inference features, making it also less-verbose than Java. It also advoids many of the confusing pitfals of Scala. Google recently made it a first-class language on Android, so it is sure to rise very quickly as a popular language.