in_array() and multidimensional array

Question

I use in_array() to check whether a value exists in an array like below,

$a = array("Mac", "NT", "Irix", "Linux");
if (in_array("Irix", $a)) 
{
    echo "Got Irix";
}

//print_r($a);

but what about an multidimensional array (below) - how can I check that value whether it exists in the multi-array?

$b = array(array("Mac", "NT"), array("Irix", "Linux"));

print_r($b);

or I shouldn't be using in_array() when comes to the multidimensional array?

Answer 1

in_array() does not work on multidimensional arrays. You could write a recursive function to do that for you:

function in_array_r($needle, $haystack, $strict = false) {
    foreach ($haystack as $item) {
        if (($strict ? $item === $needle : $item == $needle) || (is_array($item) && in_array_r($needle, $item, $strict))) {
            return true;
        }
    }

    return false;
}

Usage:

$b = array(array("Mac", "NT"), array("Irix", "Linux"));
echo in_array_r("Irix", $b) ? 'found' : 'not found';