PHP Splitting an Array into two arrays - keys arra

问题:

Is there an easy way to split an array into two arrays, one consisting of all the keys and the other consisting of all the values? This would be a reverse to the action of array_combine. Is there an inbuilt function for doing such a task? Let's use an example array:

$array = array('Tiger' => 'Forest', 'Hippo' => 'River', 'Bird' => 'Sky');

Is there a function that will split the above array into:

$array_keys = array('Tiger', 'Hippo', 'Bird');
$array_values = array('Forest', 'River', 'Sky');

回答1:

There are two functions called array_keys and array_values:

$array_keys = array_keys($array);
$array_values = array_values($array);

回答2:

There are two functions actually:

$keys = array_keys($array);
$values = array_values($array);

You can also do the exact opposite:

$array = array_combine($keys, $values);

回答3:

use array_keys and array_values

回答4:

Unfortunately there is no built-in inverse of array_combine. There is also no way to define one, since array_combine expects multiple parameters and we can't return multiple values from a function.

We can construct an alternative to array_combine which takes a single argument: the array of keys and the array of values wrapped up together in another array. This transformation is called "uncurrying" and is performed by the "call_user_func_array" function:

$array_comb  = function($arr) { return call_user_func_array('array_combine', $arr); };

This alternative function does have an inverse:

$array_split = function($arr) { return array(array_keys($arr), array_values($arr)); };

If we define function composition:

$compose  = function($f, $g) {
    return function($x) use ($f, $g) { return $f($g($x)); };
};

Then the following functions are all (extensionally) equal, ie. they all return their argument unchanged:

$identity      = function($x) { return $x; };
$left_inverse  = $compose($array_split, $array_comb);  // Split then combine
$right_inverse = $compose($array_comb, $array_split);  // Combine then split

Note that they accept different argument types though:

• $identity will work on anything.
• $left_inverse will work on any array.
• $right_inverse will work on arrays-of-arrays, where the outer array contains 2 elements, both inner arrays are of equal length and the first inner array only contains integers and strings.

回答5:

Strangely enough, the functions you're looking for are called array_keys() and array_values().

$keys = array_keys($array);
$vals = array_values($array);

回答6:

function array_split($data)
{
  $x = 0;//Counter to ensure accuracy
  $retArray[0] = array();//Array of Keys
  $retArray[1] = array();//Array of Values

  foreach($data as $key => $value)
  {
    $retArray[0][$x] = $key;
    $retArray[1][$x] = $value;
    $x++;
  }

  RETURN $retArray;
}

$data = array("key" => "value", "key2" => "value2");

$splitData = array_split($data);

//print_r($splitData[0]);//Output: Array ( [0] => key [1] => key2 ) 
//print_r($splitData[1]);//Output: Array ( [0] => value [1] => value2 ) 

print_r($splitData);
//Output:
/*
Array
(
    [0] => Array
        (
            [0] => key
            [1] => key2
        )

    [1] => Array
        (
            [0] => value
            [1] => value2
        )

)
*/