PHP - Extracting a property from an array of objects

user_133327 0
Viewed 153614

I've got an array of cats objects:

$cats = Array
    (
        [0] => stdClass Object
            (
                [id] => 15
            ),
        [1] => stdClass Object
            (
                [id] => 18
            ),
        [2] => stdClass Object
            (
                [id] => 23
            )
)

and I want to extract an array of cats' IDs in 1 line (not a function nor a loop).

I was thinking about using array_walk with create_function but I don't know how to do it.

Any idea?

php
10 Answers

Warning create_function() has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged.

You can use the array_map() function.
This should do it:

$catIds = array_map(create_function('$o', 'return $o->id;'), $objects);

As @Relequestual writes below, the function is now integrated directly in the array_map. The new version of the solution looks like this:

$catIds = array_map(function($o) { return $o->id;}, $objects);
user_241810 
function extract_ids($cats){
    $res = array();
    foreach($cats as $k=>$v) {
        $res[]= $v->id;
    }
    return $res
}

and use it in one line:

$ids = extract_ids($cats);
user_128550

Warning create_function() has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged.

Builtin loops in PHP are faster then interpreted loops, so it actually makes sense to make this one a one-liner:

$result = array();
array_walk($cats, create_function('$value, $key, &$result', '$result[] = $value->id;'), $result)
soulmerge_445620

CODE

<?php

# setup test array.
$cats = array();
$cats[] = (object) array('id' => 15);
$cats[] = (object) array('id' => 18);
$cats[] = (object) array('id' => 23);

function extract_ids($array = array())
{
    $ids = array();
    foreach ($array as $object) {
        $ids[] = $object->id;
    }
    return $ids;
}

$cat_ids = extract_ids($cats);
var_dump($cats);
var_dump($cat_ids);

?>

OUTPUT

# var_dump($cats);
array(3) {
  [0]=>
  object(stdClass)#1 (1) {
    ["id"]=>
    int(15)
  }
  [1]=>
  object(stdClass)#2 (1) {
    ["id"]=>
    int(18)
  }
  [2]=>
  object(stdClass)#3 (1) {
    ["id"]=>
    int(23)
  }
}

# var_dump($cat_ids);
array(3) {
  [0]=>
  int(15)
  [1]=>
  int(18)
  [2]=>
  int(23)
}

I know its using a loop, but it's the simplest way to do it! And using a function it still ends up on a single line.

user_561900 
// $array that contain records and id is what we want to fetch a
$ids = array_column($array, 'id');
user_114809720

The create_function() function is deprecated as of php v7.2.0. You can use the array_map() as given,

function getObjectID($obj){
    return $obj->id;
}

$IDs = array_map('getObjectID' , $array_of_object);

Alternatively, you can use array_column() function which returns the values from a single column of the input, identified by the column_key. Optionally, an index_key may be provided to index the values in the returned array by the values from the index_key column of the input array. You can use the array_column as given,

$IDs = array_column($array_of_object , 'id');
user_82033570
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