Description:
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If the upload_tmp_dir is a symlink, file_exists() doesn't work after a realpath() call. In my server the default /tmp is a symlink to /home/tmp. It works if i change the upload_tmp_dir to the /home/tmp. (safe_mode on)

Reproduce code:
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    $t = $_FILES["uf"]["tmp_name"];
// $t = /tmp/phpAbcde
// realpath($t) = /home/tmp/phpAbcde
    var_dump(file_exists($t)); // true
    var_dump(file_exists(realpath($t))); // false
    var_dump(is_file($t)); // true
    var_dump(is_file(realpath($t))); // false


Expected result:
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I got false when i called the file_exists() and is_file() with realpath($t).