If you never ever touched any of these technologies you should use the easiest one.
Your priority should be like this, I will rank then from according to their usability/simplicity:
By far simpliest of them all. In a matter of days you can learn more then enough to create your basic server. No matter do you want to handle only REST calls or do full a page creation on a server side.
It has largest overall support and you will easily find hosting, if you already don't have it. It works on all current desktop OS's like Windows, Linux and MacOS.
Not that much. If I have to think of any I would say that it is a smaller brother of Java and .NET.
My favorite, more secure (but not that much secure) then PHP. It requires much more time to handle and use right. Like with Java I prefer its syntax over PHP. Still more readable syntax then Java, specially if you delve into something more complex.
But, as it is a Microsoft technology it will run only on a Windows platform. Skipp it if this is a turn off for you.
Almost best of both worlds. Better and more powerful syntax then PHP and unlike .NET you can run it on any available platform. Like .NET it requires more time to master correctly then PHP.
Java is usually used in large corporate projects and you will not find that much help over some basic stuff and usage. Even if you master it correctly you will still need to delve into Java EE if you want to create anything decent and robust, basically it is a largest time sink if you only need to create one server application. Other problem is memory consumption, that is why you will see much less available Java hosting platforms the it is case with .NET and PHP.
If you don't have that much time and you are not sure you are ever going to use it again then stick to PHP. If you are planing on using this technology for a longer period then stick to .NET. And finally if you are going to use it in a longer period but Windows platform is a turn off then stick to Java.