User Contributed Notes

1. Skip to note 4 content

   
   Barbara Ford
   
   
   11 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 5 content

   
   bcworkz
   
   
   10 years ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 9You 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.

3. Skip to note 6 content

   
   wbeaumo
   
   
   11 months ago
   

   You must log in to vote on the helpfulness of this noteVote results for this note: 2You must log in to vote on the helpfulness of this note

   This is functionally identical to the built-in (as of PHP 5.5) function array_column(), except that wp_list_pluck() does NOT check if $field is a key/property in each item of $input_list. If the key/property doesn’t exist in an item, null will be added to the new array and a warning will be generated, whereas array_column() simply won’t add a value at all. If you prefer the former behavior, just be aware that use of this function could lead to warnings being output (depending on whether WordPress or your server environment is configured to display errors). Otherwise you should use array_column(). Also, if you use $index_key and an item’s value at $index_key is an array or object then a TypeError will be thrown, bringing the whole page to a halt if it isn’t caught (same as with array_column()).