If you use PHP to change the uploaded file to its MD5 value and retain the suffix name

Suppose I use PHP to receive the form upload file, how to do to the uploaded file name (change to its file MD5 value, to prevent duplicate names), and retain the suffix.
It's best to give a sample code

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Suppose I use PHP to receive the form upload file, how to do to the uploaded file name (change to its file MD5 value, to prevent duplicate names), and retain the suffix.
It's best to give a sample code

Suppose the form is:

This will change the name:
$str = ' test.name ';
$pos =strrpos ($str, '. ' ）；
Echo Substr_replace ($STR, MD5 (substr ($str, 0, $pos)), 0, $pos);
Mobile phone writing code is very laborious ...

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