php类名称区分大小写

I declare a class like this in php

<?php class Db(){  //something}

php has a class with name DB

when I run this code on linux OS , it works but when run it on windows, return a Fatal error.

Is php class name insensitive? if is insensitive , why run on linux? if is case sensitive , why dose not run on windows?

Don't use PEAR, it time to go with composer if you can., for your issue you can check before defining class, if its exist extend it

if(class_exists('DB') != true)
  {
    class Db extends DB
    ...
    ...
    ... 
  }

or go with Namespace on php 5.3

namespace Core;
class Db {}

to call

\Core\Db::from();

or simply change the name of class

hope it helps