在webpack localhost中找不到PHP文件

Hi so I have the following js code making call to mail.php

$.ajax({
    url: 'mail.php',
    type: 'post',
    data: $this.serialize(),
    success: function (data) {

        if ( isJSON(data) ) {
            // do something
        } else {
            // do something
        }       
    },
    error: function(){
            // do something
        }
    });

When the ajax call is made: in my console it says POST http://localhost:8080/mail.php 404 (Not Found), and a XHR Response says: Cannot POST /mail.php

A similar post which mentions checking if the file in the same directory, it is. When I manually type out the url localhost:8080/mail.php it downloads the file. I have php installed, I am running in webpack-dev and react.