Constant CAKE_CORE_INCLUDE_PATH already defined CakePHP

I am a beginner to CakePHP, I just got a code of the project to make some minor changes into the project, but as I copy and paste the project files into my wamp server and changed my database constants according to my localhost, I got error and website site is not even loading properly no css no js.

I am using 2.5 CakePHP Version and 5.6 PHP version

The complete error message is

( ! ) Notice: Constant CAKE_CORE_INCLUDE_PATH already defined in C:\wamp64\www\cakephp2.5\app\webroot\index.php on line 64
Call Stack

Time Memory Function Location

1 0.0007 242672 {main}( ) …\index.php:0
2 0.0015 265256 require( ‘C:\wamp64\www\cakephp2.5\app\webroot\index.php’ ) …\index.php:41
3 0.0015 265488 define ( ) …\index.php:64