Change language selection text based on browser language? [duplicate]

This question already has an answer here:

• JavaScript for detecting browser language preference 14 answers

I have a basic dropdown menu where the user is able to select the language the website should appear in. My problem is not everyone understands "Select Language". So I was trying to find a method that allows to detect the language of the browser and serve an appropiate text accordingly.

For example if:

User Agent is in English

then:

"Select Language"

How do I do this with PHP or Javascript?