wp_list_pluck( array $input_list, int|string $field, int|string $index_key = null ): array

User Contributed Notes

1. Skip to note 3 content

   Barbara Ford 10 years ago

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   This is an example of how to use this function.

   The following is an array listing foods:

   $foods = array(
   	array(
   		'name'  => 'Banana',
   		'color' => 'Yellow',
   	),
   	array(
   		'name'  => 'Apple',
   		'color' => 'Red',
   	),
   	array(
   		'name'  => 'Lettuce',
   		'color' => 'Green',
   	),
   	array(
   		'name'  => 'Apple',
   		'color' => 'Red',
   	),
   );

   The names of each food can easily be “plucked” from the $foods array using wp_list_pluck() .

   $food_names = wp_list_pluck( $foods, 'name' ); 

   $food_names will now contain a numerically indexed array of food names equivalent to:

   array(
   	'Banana',
   	'Apple',
   	'Lettuce',
   	'Apple'
   );
2. Skip to note 4 content

   bcworkz 9 years ago

   You must log in to vote on the helpfulness of this noteVote results for this note: 8You must log in to vote on the helpfulness of this note

   Use of the $index_key argument is best reserved for unique or index fields, otherwise data could be missing from the returned array. Consider this modified $foods list from the previous example:

   $foods = array(
       array(
           'name'  => 'Banana',
           'color' => 'Yellow',
       ),
       array(
           'name'  => 'Apple',
           'color' => 'Red',
       ),
       array(
           'name'  => 'Kiwi',
           'color' => null,
       ),
       array(
           'name'  => 'Lettuce',
           'color' => 'Green',
       ),
       array(
           'name'  => 'Cherry',
           'color' => 'Red',
       ),
   );

   Using ‘color’ as $index_key is questionable.

   $food_names = wp_list_pluck( $foods, 'name', 'color' );

   $food_names contains an associative array equivalent to:

   array(
       'Yellow' => 'Banana',
       'Red'    => 'Cherry',
        0       => 'Kiwi',
       'Green'  => 'Lettuce',
   )

   The ‘Apple’ value was overwritten by the subsequent ‘Cherry’ since they both had a ‘Red’ index key value. Since ‘Kiwi’ had an unusable color value, its key is simply indexed.