How to search by key=>value in a multidimensional array in PHP

Code:

function search($array, $key, $value){    $results = array();    if (is_array($array)) {        if (isset($array[$key]) && $array[$key] == $value) {            $results[] = $array;        }        foreach ($array as $subarray) {            $results = array_merge($results, search($subarray, $key, $value));        }    }    return $results;}$arr = array(0 => array(id=>1,name=>"cat 1"),             1 => array(id=>2,name=>"cat 2"),             2 => array(id=>3,name=>"cat 1"));print_r(search($arr, 'name', 'cat 1'));

Output:

Array(    [0] => Array        (            [id] => 1            [name] => cat 1        )    [1] => Array        (            [id] => 3            [name] => cat 1        ))

If efficiency is important you could write it so all the recursive calls store their results in the same temporary $results array rather than merging arrays together, like so:

function search($array, $key, $value){    $results = array();    search_r($array, $key, $value, $results);    return $results;}function search_r($array, $key, $value, &$results){    if (!is_array($array)) {        return;    }    if (isset($array[$key]) && $array[$key] == $value) {        $results[] = $array;    }    foreach ($array as $subarray) {        search_r($subarray, $key, $value, $results);    }}

The key there is that search_r takes its fourth parameter by reference rather than by value; the ampersand & is crucial.

FYI: If you have an older version of PHP then you have to specify the pass-by-reference part in the call to search_r rather than in its declaration. That is, the last line becomes search_r($subarray, $key, $value, &$results).

How about the SPL version instead? It'll save you some typing:

// I changed your input example to make it harder and// to show it works at lower depths:$arr = array(0 => array('id'=>1,'name'=>"cat 1"),             1 => array(array('id'=>3,'name'=>"cat 1")),             2 => array('id'=>2,'name'=>"cat 2"));//here's the code:    $arrIt = new RecursiveIteratorIterator(new RecursiveArrayIterator($arr)); foreach ($arrIt as $sub) {    $subArray = $arrIt->getSubIterator();    if ($subArray['name'] === 'cat 1') {        $outputArray[] = iterator_to_array($subArray);    }}

What's great is that basically the same code will iterate through a directory for you, by using a RecursiveDirectoryIterator instead of a RecursiveArrayIterator. SPL is the roxor.

The only bummer about SPL is that it's badly documented on the web. But several PHP books go into some useful detail, particularly Pro PHP; and you can probably google for more info, too.

<?php$arr = array(0 => array("id"=>1,"name"=>"cat 1"),             1 => array("id"=>2,"name"=>"cat 2"),             2 => array("id"=>3,"name"=>"cat 1"));$arr = array_filter($arr, function($ar) {   return ($ar['name'] == 'cat 1');   //return ($ar['name'] == 'cat 1' AND $ar['id'] == '3');// you can add multiple conditions});echo "<pre>";print_r($arr);?>

Ref: http://php.net/manual/en/function.array-filter.php