Questions about the phpfilesize function

Phpfilesize function problems in linux why can I use filesize to upload files to a temporary folder? sometimes, the file cannot be obtained. you must first confirm that the file exists, is the path not sent? Wrong. this is impossible. you do not have the required permissions. The file size cannot be obtained ., Print_r ($ _ FILES); check the cause of the php filesize function.
In linux, why can I use filesize to obtain files uploaded to temporary folders? sometimes, the files cannot be obtained.
No.

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Make sure the file exists first.
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Is the path not sent? Wrong
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This is not possible. you do not have the required permissions. The file size cannot be obtained.
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Print_r ($ _ FILES );
Let's see why.