按第二个数组中的值过滤数组

Question

** I have edited this to show how I got my code to work using array_search

I have an array, $arr1 with 5 columns as such:

 key    id  name    style   age whim
 0      14  bob     big     33  no
 1      72  jill    big     22  yes
 2      39  sue     yes     111 yes
 3      994 lucy    small   23  no
 4      15  sis     med     24  no
 5      16  maj     med     87  yes
 6      879 Ike     larg    56  no
 7      286 Jed     big     23  yes

This array is in a cache, not a database.

I then have a second array with a list of id values -

$arr2 = (0=>14, 1=>72, 2=>8790)

How do I filter $arr1 so it returns only the rows with the id values in $arr2?

I got my code to work as follows:

$arr1 = new CachedStuff();  // get cache

$resultingArray = [];  // create an empty array to hold rows
$filter_function = function ($row) use ($arr2) {
    return (array_search($row['id'], $arr2));
};
$resultingArrayIDs = $arr1->GetIds($filter_function, $resultingArray);

This gives me two outputs: $resultingArray & $resultingArrayIDs both of which represent the intersection of the $arr1 and $arr2.

Answer 1

The trouble with using iterated checks on the second/filtering array is that it will lose efficiency as the arrays' sizes increase.

By assigning new keys to the first array, and flipping the filtering array's values to keys, you run a one-time filter/intersect on the arrays and then reindex the output array.

My method calls no foreach() loops and has no iterated conditionals.

Code: (Demo)

$arr1=[
    ['key'=>0,'id'=>14,'name'=>'bob','style'=>'big','age'=>33,'whim'=>'no'],
    ['key'=>1,'id'=>72,'name'=>'jill','style'=>'big','age'=>22,'whim'=>'yes'],
    ['key'=>2,'id'=>39,'name'=>'sue','style'=>'yes','age'=>111,'whim'=>'yes'],
    ['key'=>3,'id'=>994,'name'=>'lucy','style'=>'small','age'=>23,'whim'=>'no'],
    ['key'=>4,'id'=>15,'name'=>'sis','style'=>'med','age'=>24,'whim'=>'no'],
    ['key'=>5,'id'=>16,'name'=>'maj','style'=>'med','age'=>87,'whim'=>'yes'],
    ['key'=>6,'id'=>879,'name'=>'Ike','style'=>'larg','age'=>56,'whim'=>'no'],
    ['key'=>7,'id'=>286,'name'=>'Jed','style'=>'big','age'=>23,'whim'=>'yes']
];
$arr2=[14,72,879];

$arr1=array_column($arr1,null,'id');  // generate temporary keys
//var_export($arr1);

$arr2=array_flip($arr2);  // move values to keys
//var_export($arr2);

$filtered=array_intersect_key($arr1,$arr2);  // retain subarrays that qualify
//var_export($filtered);

$reindexed=array_values($filtered);  // reindex array
var_export($reindexed);

or written as a one-liner like this:

var_export(array_values(array_intersect_key(array_column($arr1,null,'id'),array_flip($arr2))));

Output:

array (
  0 => 
  array (
    'key' => 0,
    'id' => 14,
    'name' => 'bob',
    'style' => 'big',
    'age' => 33,
    'whim' => 'no',
  ),
  1 => 
  array (
    'key' => 1,
    'id' => 72,
    'name' => 'jill',
    'style' => 'big',
    'age' => 22,
    'whim' => 'yes',
  ),
  2 => 
  array (
    'key' => 6,
    'id' => 879,
    'name' => 'Ike',
    'style' => 'larg',
    'age' => 56,
    'whim' => 'no',
  ),
)