Extract values of a certain type within a multi-dimensional array in PHP

Question

Does anyone know how to extract arrays that of a certain type from a larger array? For example, consider these results from a var_dump():

     [0]=>
      array(5) {
        ["post"]=>
        string(60) "Paris"
        ["capacity"]=>
        string(5) "58515"
        ["region"]=>
        string(60) "WHA"
        ["seats"]=>
        string(2) "55"
        ["growth"]=>
        string(4) "3880"
      }
      [1]=>
      array(5) {
        ["post"]=>
        string(60) "Tel Aviv"
        ["capacity"]=>
        string(6) "530910"
        ["region"]=>
        string(60) "NEA"
        ["seats"]=>
        string(2) "65"
        ["growth"]=>
        string(4) "3267"
      }
      [2]=>
      array(5) {
        ["post"]=>
        string(60) "Paris"
        ["capacity"]=>
        string(6) "962115"
        ["region"]=>
        string(60) "EUR"
        ["seats"]=>
        string(2) "11"
        ["growth"]=>
        string(4) "2660"
      }

I am sure this may seem simple to some that live in the 5th dimension, but I am having a devil of a time extracting arrays where region = "WHA" within my foreach() to try and build a separate array with just the WHA data.

foreach($data as $keys => $datums){
    //Planning to build JSON string
    if($datums['region'] == "WHA"){
        //Some processing
    }
}

The result should look like this:

  [0]=>
  array(5) {
    ["post"]=>
    string(60) "Paris"
    ["capacity"]=>
    string(5) "58515"
    ["region"]=>
    string(60) "WHA"
    ["seats"]=>
    string(2) "55"
    ["growth"]=>
    string(4) "3880"
  }

I have tried all kinds of different things like looking at array_filter that are just not working for me, and I am just concerned about what the right way looks like. Any ideas? Much appreciated.

I don't really see where you are stuck? You can do it of course like you already do it with a foreach loop and add the array: if($datums['region'] == "WHA"){ $result[] = $datums; }. Or also with array_filter(), e.g. $result = array_filter($yourArray, function($v){return $v["region"] == "WHA";}); (btw: I live in the 4th dimension :) — Rizier123
– Rizier123, Commented Jan 7, 2016 at 23:17

Octopus · Accepted Answer · 2016-01-07 23:44:00Z

1

If I understand correctly, I believe you want to build a new array that only contains the elements from the first array that pass a test. The following example does that and produces a JSON encoded string of that data:

$new = Array();
foreach($data as $key => $datum){
    //Planning to build JSON string
    if ( $datum['region']=='WHA') {
        $new[] = $datum;
    }
}
$out = json_encode($new);

answered Jan 7, 2016 at 23:44

Octopus

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2 Comments

Mr. Concolato Over a year ago

I used array_push($new, $datums); and got what I wanted as there are many arrays with WHA as the region. I know I was close. Must have been tired :). Thanks for the tip @Octopus.

Octopus Over a year ago

array_push($haystack,$needle) does exactly the same as $haystack[] = $needle

Typel · Accepted Answer · 2016-01-08 00:02:22Z

You could also encapsulate this in a function

<?php
function filterArray($arr, $index, $filter) {
    foreach( $arr as $key=>$elem ) {
        if ( $elem[$index] != $filter ) {
            unset($arr[$key]);
            }
        }
    return $arr;
    }
?>

If $YourArray is the OP's array, you could use this to filter out any item in the array which does not have an indexed element for "region" which equals "WHA"

$filtered = filterArray($yourArray, "region", "WHA");

An alternative version of this would use an ampersand (&) to pass a pointer to the original array. For example, if you used this as your function declaration:

function filterArray(&$arr, $index, $filter) {

then you no longer need to set a destination for the returned array, because the original array actually gets modified directly by the function.

filterArray($yourArray, "region", "WHA");

Nyranith · Accepted Answer · 2016-01-08 00:09:20Z

1

Think this should fix your code.

foreach($data as $keys => $datums){
    //Planning to build JSON string
    if(isset($datums["region"]) && strcmp($datums["region"], "WHA") === 0){
        //Some processing
     }
 }

edited Jan 8, 2016 at 0:09

answered Jan 7, 2016 at 23:22

Nyranith

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3 Comments

Rizier123 Over a year ago

Why should OP use double quotes for the array index? Makes no difference if ' or "

Nyranith Over a year ago

I know it should not matter, but I have had problems with it :)

randrade86 Over a year ago

You can use the faster === if you don't need to know which string is greater. See this link

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