Brother, I input Chinese characters in the text box, but when reading the data in the php program, it prompts garbled characters.

I enter Chinese characters in the text box, but when the data is read in the PHP program, it prompts garbled characters
I enter Chinese characters in the text box, but when the data is read in the PHP program, it prompts garbled characters. Additional questions: My database and A different encoding is used on the web page. The code also uses an iconv() function for conversion, but when debugging, it still prompts garbled characters. Please tell me how to solve it?

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Modify the browser’s encoding, determine the header encoding, and determine the encoding of the php file.

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Please Give the main code snippet