为什么我不能实例化这个类？

Question

Trying to build a simple oop solution but can't understand why I can't instantiate this class. I'm using an interface, class and implementing the class on an index.php but I'm getting a not found class error. What am I doing wrong?

Interface:

namespace interfaces;

interface ISales
{
}

Class:

namespace classes;

use interfaces\iSales;

class Sales implements iSales
{
}

Implementation (index.php):

use classes\Sales;

$sales = new Sales();

Error:

PHP Fatal error:  Uncaught Error: Class 'classes\Sales' not found in ...

Error: Class 'classes\Sales' not found in

Answer 1

Thanks for all the comments. I've just used composer for that using this example: https://enterprise-level-php.com/2017/12/25/the-magic-behind-autoloading-php-files-using-composer.html

I'm coming from C# so PHP works a little bit different.