Question about automatic namespace loading

Running environment description: foo. php (file2) is referenced in the index. php (file1) file. if you declare the namespacetestindex in index. php, an error is returned.

Running environment description:
Reference foo. php (file2) in the index. php (file1) file)
Problem:
If you declare the namespace testindex in index. php, an error is returned.

Reply content:

Running environment description:
Reference foo. php (file2) in the index. php (file1) file)
Problem:
If you declare the namespace testindex in index. php, an error is returned.

Because you add a namespace to the function_ Autoload ()It is also used in this namespace, that is, calling this function becomes\ Test \ index \__ autoload ()Php cannot be found._ Autoload ()This function cannot complete the automatic loading process.

One is the result of the annotated namespace, and the other is not.
Why is this happening?
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