Скачать или смотреть Resolving React and Yii2 Connection Error: Missing Access-Control-Allow-Origin Header

Learn how to fix the `Access-Control-Allow-Origin` header issue when connecting React and Yii2. This guide provides easy steps to resolve CORS errors effectively.
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Resolving React and Yii2 Connection Error: Missing Access-Control-Allow-Origin Header

When developing applications that use React as the front-end and Yii2 as the back-end, you may encounter frustrating errors related to CORS (Cross-Origin Resource Sharing). One common error is: "No 'Access-Control-Allow-Origin' header is present on the requested resource." This issue prevents your front-end from successfully communicating with the back-end, halting the application's functionality. Here, we'll explore why this error occurs and how to resolve it effectively.

Understanding CORS and the Issue

CORS is a security feature that allows or restricts resources (like APIs) to be requested from a different origin than the one that served the initial web page. When your React application attempts to access API endpoints hosted on a different domain (like those served by Yii2), the browser checks for specific CORS headers in the response.

If these headers are not present, as is the case with the error you might see, the request is blocked. The key header to address here is Access-Control-Allow-Origin, which specifies which domains are permitted to access your resources.

Enabling CORS in Yii2

To resolve the error you are facing, you'll need to enable CORS on your Yii2 API. This can be accomplished by adding a CORS filter to your controller's behaviors. Follow these steps:

Step 1: Modify the Controller

Open your MainPageController, and you will need to add a method called behaviors(). This method defines the behaviors that your controller will use, including the CORS configuration.

Here’s how to implement it:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Explanation of Each Configuration

Origin: Specifies which domains are allowed to access your resources. For development, you can set it to your local React app's URL (http://localhost:3000), and for production replace with your actual domain.

Access-Control-Request-Method: Defines which HTTP methods are allowed for CORS requests, including GET, HEAD, POST, and PUT in this case.

Access-Control-Request-Headers: Specifies which headers can be included in the actual request. This is important for security purposes.

Access-Control-Allow-Credentials: If set to true, this allows credentials (like cookies or authorization headers) to be included in requests sent to the server.

Access-Control-Max-Age: Indicates how long the results of a preflight request can be cached.

Access-Control-Expose-Headers: Allows the browser to access the specified headers in the response.

Step 3: Test Your Changes

Once you've added the above CORS settings to your Yii2 controller, test your React application again. The connection error should be resolved, allowing seamless communication between your front-end and back-end.

Conclusion

Encountering CORS errors between a React front-end and a Yii2 back-end can be frustrating, but with the right configurations, you can quickly resolve them. By applying the CORS filter in your Yii2 controller, you not only enable necessary headers but also enhance your application's robustness. Always remember to adjust the allowed origins appropriately when moving to production.

If these changes do not fix the issue, ensure that your server is correctly configured to handle CORS requests. Happy coding!