How to Handle Cross-Domain Requests in PHP: JSONP vs CORS Explained

1. Background of Cross-Origin Data Transmission

In modern frontend development, it's common to need data from a different domain via AJAX. Due to browser security policies, direct access to resources across domains is restricted. Therefore, solving cross-origin communication has become an essential task. This article introduces two popular PHP-based solutions: JSONP and CORS.

2. Understanding the Same-Origin Policy

The Same-Origin Policy is a fundamental browser security measure. It restricts JavaScript from accessing resources unless the protocol, domain, and port of the request match those of the current page. For example, if the page is loaded from http://www.example.com/index.html:

• Protocol must be http
• Domain must be www.example.com
• Port must be 80 (default if not specified)

3. Implementing Cross-Domain with JSONP

JSONP (JSON with Padding) is a legacy method that uses the