Answer 1, Authority 100%
No Php, it is impossible. On JS you can and there are two ways. You can do through WebView – it’s just essentially an application-site application using HTML, CSS, etc, incl. Js. The project you need in this case is Apache Cordova. And you can get acquainted with REACT NATIVE technology and make native applications on JS. But information on this issue is very little, even in English.
From what you write seemingly such a scenario: JS for mobile application, PHP for backend.
But now, if you wish, you can find anything as for a mobile application (I will not be surprised if some enthusiast saw an analogue of the idea of ReactNative, only on some brainfuck or COW) and for the server part.
It is more important to determine what you need that you can and choose the desired tool. If you need something simple, how to send / get information, display it / save, do not need a Pixel-Perfect design, etc., you do not want to touch Objective-C / SWIFT / Java / Kotlin – Take React Native and Write on js. You want to delve into some features of mobile – take Cordova and, you can say, show the mobile version of the site.