'Check if specific array key exists in multidimensional array - PHP

I have a multidimensional array e.g. (this can be many levels deep):

$array = Array ( 
    [21] => Array ( ) 
    [24] => Array ( 
        [22] => Array ( ) 
        [25] => Array ( 
            [26] => Array ( ) 
        ) 
    ) 
)

I am trying to loop through it to see if a certain key exists:

$keySearch = 22; // key searching for

function findKey($array, $keySearch) {
    foreach ($array as $item){
        if (isset($item[$keySearch]) && false === findKey($item[$keySearch], $item)){
            echo 'yes, it exists';
        }
    }
}

findKey($array, $keySearch);

But it finds nothing. Is there an error in the loop?

phparraysmultidimensional-array


Solution 1:[1]

array_key_exists() is helpful.

Then something like this:

function multiKeyExists(array $arr, $key) {

    // is in base array?
    if (array_key_exists($key, $arr)) {
        return true;
    }

    // check arrays contained in this array
    foreach ($arr as $element) {
        if (is_array($element)) {
            if (multiKeyExists($element, $key)) {
                return true;
            }
        }

    }

    return false;
}

Working example: http://codepad.org/GU0qG5su

Solution 2:[2]

Here is a one line solution:

echo strpos(json_encode($array), $key) > 0 ? "found" : "not found";

This converts the array to a string containing the JSON equivalent, then it uses that string as the haystack argument of the strpos() function and it uses $key as the needle argument ($key is the value to find in the JSON string).

It can be helpful to do this to see the converted string: echo json_encode($array);

Be sure to enclose the needle argument in single quotes then double quotes because the name portion of the name/value pair in the JSON string will appear with double quotes around it. For instance, if looking for 22 in the array below then $key = '"22"' will give the correct result of not found in this array:

$array =
Array ( 
        21 => Array ( ), 
        24 => 
        Array ( 
            522 => Array ( ),
            25 =>
                Array ( 
                26 => Array ( ) 
            )
        )
    );

However, if the single quotes are left off, as in $key = "22" then an incorrect result of found will result for the array above.

EDIT: A further improvement would be to search for $key = '"22":'; just incase a value of "22" exists in the array. ie. 27 => "22" In addition, this approach is not bullet proof. An incorrect found could result if any of the array's values contain the string '"22":'

Solution 3:[3]

function findKey($array, $keySearch)
{
    // check if it's even an array
    if (!is_array($array)) return false;

    // key exists
    if (array_key_exists($keySearch, $array)) return true;

    // key isn't in this array, go deeper
    foreach($array as $key => $val)
    {
        // return true if it's found
        if (findKey($val, $keySearch)) return true;
    }

    return false;
}

// test
$array = Array ( 
    21 => Array ( 24 => 'ok' ),
    24 => Array ( 
        22 => Array ( 29 => 'ok' ),
        25 => Array ( 
            26 => Array ( 32 => 'ok' ) 
        )
    )
);

$findKeys = Array(21, 22, 23, 24, 25, 26, 27, 28, 29, 30);
foreach ($findKeys as $key)
{
    echo (findKey($array, $key)) ? 'found ' : 'not found ';
    echo $key.'<br>';
}

Solution 4:[4]

returns false if doesn't exists, returns the first instance if does;

function searchArray( array $array, $search )
{
    while( $array ) {
        if( isset( $array[ $search ] ) ) return $array[ $search ];
            $segment = array_shift( $array );
            if( is_array( $segment ) ) {
                if( $return = searchArray( $segment, $search ) ) return $return;
            }
        }
    }
    return false;
}

Solution 5:[5]

For sure some errors, is this roughly what you are after? (Untested code):

$keySearch=22; // key seraching for

function findKey($array, $keySearch) 
{ 
    // check whether input is an array
    if(is_array($array)
    {
       foreach ($array as $item)
       {
         if (isset($item[$keySearch]) || findKey($item, $keysearch) === true)
          {
            echo 'yes, it exists';
            return true;
          }
       }
    }
}

Solution 6:[6]

Here is one solution that finds and return the value of the key in any dimension array..

function findValByKey($arr , $keySearch){
    $out = null;
    if (is_array($arr)){
        if (array_key_exists($keySearch, $arr)){
            $out = $arr[$keySearch];
        }else{
            foreach ($arr as $key => $value){
                if ($out = self::findValByKey($value, $keySearch)){
                    break;
                }
            }
        }
    }
    return $out;
}

Solution 7:[7]

function arrayKeyExsits($array, $keyPath): bool {
    $keys = explode('=>', $keyPath);
    if (count($keys) === 1) {
        return array_key_exists($keyPath, $array);
    } else {
        $key = array_shift($keys);
        if (array_key_exists($key, $array)) {
            return arrayKeyExsits($array[$key], implode('=>', $keys));
        } else {
            return false;
        }
    }
}

$array = [
    'level1' => [
        'level2' => [
            'level3' => [
             ]
        ]
    ]
];

var_dump(arrayKeyExists($array, 'level1')) // true
var_dump(arrayKeyExists($array, 'level1=>level2')) // true
var_dump(arrayKeyExists($array, 'level1=>level2=>level3')) // true

var_dump(arrayKeyExists($array, 'foo')) // false
var_dump(arrayKeyExists($array, 'level1=>foo=>level3')) // false

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1
Solution 2
Solution 3 minboost
Solution 4 Luke Snowden
Solution 5 Pradeep
Solution 6 Mohammad Ali Fathi
Solution 7 d4nni5

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