How does php set the key of array to be equal to the value?

How does php set the key of array to be equal to value? the following Array array ([0] = & gt; content 1 [1] = & gt; content 2 [2] = & gt; content 3) the following Array (& quot; content 1 & quot; = & gt; & quot; content 1 & quot;, & quot; content 2 & quot php how to set the array key to be equal to the value
The following array is available:
Array ([0] => Content 1 [1] => content 2 [2] => Content 3)

The following array is expected to be produced after processing

Array ("content 1" => "content 1", "content 2" => "content 2", "Content 3" => "content 3 ")

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Foreach traverses the array and then uses the for loop to loop with the key value.
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PHP code

$ Arr = array (0 => 'Content 1', 1 => 'Content 2', 2 => 'Content 3'); foreach ($ arr as $ v) $ k [] = $ v; print_r (array_combine ($ k, $ arr ));
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PHP code

   
   
$ Arr = array (0 => 'Content 1', 1 => 'Content 2', 2 => 'Content 3 '); $ r = array_combine (array_values ($ arr), $ arr); print_r ($ r );