Case Sensitivity in php

The names of user-defined classes and functions, as well as built-in constructs and keywords such as echo, while, class, etc., are case-insensitive. Thus, these three lines are equivalent: echo(“hello, world”);ECHO(“hello, world”);EcHo(“hello, world”); Variables, on the other hand, are case-sensitive. That is, $name, $NAME, and $NaME are three different variables