php5 upwork test answer | What is the best way to change the key without changing the value of a PHP array element?

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What is the best way to change the key without changing the value of a PHP array element?

Answers:

• $arr[$newkey] = $oldkey; unset($arr[$oldkey]);

• $arr[$newkey] = $arr[$oldkey]; unset($arr[$oldkey]);

• $newkey = $arr[$oldkey]; unset($arr[$oldkey]);

• $arr[$newkey] = $oldkey.GetValue(); unset($arr[$oldkey]);