src/Functions/AbstractFunctions.php
public function arrayKeyExistsRecursive(string $needle, array $haystack): bool
    {
        $result = array_key_exists($needle, $haystack);
        if (true === $result) {
            return $result;
        }
        $this->arrayKeyExistsRecursiveExtended($needle, $haystack);

        return $result;
    }
public function arrayKeyExistsRecursive(string $needle, array $haystack): bool
    {
        $result = array_key_exists($needle, $haystack);
        if (true === $result) {
            return $result;
        }
        $this->arrayKeyExistsRecursiveExtended($needle, $haystack);

        return $result;
    }
public function arrayKeyExistsRecursive ( string $ needle , array $ haystack ) : bool { $ result = array_key_exists ( $ needle , $ haystack ) ; if ( true === $ result ) { return $ result ; } $ this -> arrayKeyExistsRecursiveExtended ( $ needle , $ haystack ) ; return $ result ; }
Recursive version of array_key_exists.

The PHP funcction 'array_key_exists' does NOT work recursively, so this
can be used to find a key nested in a multidimensional array.
Another option is to use the 'array_walk_recursive' function since PHP 5.3.

@param string $needle   The search string
@param array  $haystack The space indented setting

@return bool The set of formatted <link> stylesheet tags

@api
Recursive version of array_key_exists .