How to generate an xml file based on the database query results using thinkphp

To generate an xml file based on the database query results, use thinkphp to generate the file. first, declare a header for xml, and then generate the desired node .. attention should be paid to encoding, and the node should be closed ., I didn't think it was so complicated when generating XML. it would be easy to concatenate characters or use s to generate xml files based on database query results. how can I generate XML files using thinkphp?
How to do this

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First, declare a header as xml
Second, generate the desired node ..
Attention should be paid to encoding, and the node should be closed.
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I didn't think it was that complicated when generating XML.

Just concatenate characters.

Very simple
You can use simplexml or thinkphp.
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I usually use phpexcel