How to implement cross-domain operations in PHP

This article mainly introduces relevant information on how PHP realizes cross-domain. It is very good and has reference value. Friends who need it can refer to it

Due to work needs, some interfaces of the client software use HTML CSS Javascript implementation, these files are placed locally on the client and loaded as local files. However, in some cases, it is necessary to connect to the server to obtain some information. If no processing is done, the request fails and the returned information is as follows:

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.

This is because browsing The server cross-domain policy takes effect and blocks cross-domain requests. Just look at the HTTP request process. When the backend is requested for the first time, the browser realizes that it is accessing a cross-resource and does not directly send a GET request to obtain data. Instead, it sends an OPTIONS request to ask whether the resource can be accessed. We call it a Preflight request. By default, due to the existence of the same-origin policy, the header returned by this request does not have the 'Access-Control-Allow-Origin' attribute, so the access fails. If you want to achieve cross-domain, the key lies in the server, and the client code can be written in the normal way. For the server, you only need to add this attribute to the returned header information where the OPTIONS request is received. The code is as follows:

header("Access-Control-Allow-Origin: *");

Note , must be set before all information is output to the client.

Summary: The above is the entire content of this article, I hope it will be helpful to everyone's study.

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