Comparing (empty) arrays in PHP

Question

I want to write a test case to make sure a function call sets an array; however, I don't find a way to compare two arrays to make sure two empty arrays are not equal.

// code to be tested (simplified)
$foo = null;
function setFoo($input) {
    global $foo;

    $foo = array(); // BUG!!! The correct line would be: $foo = $input;
}

// test code
// given
$input = array();
// when
setFoo($input);
// then
if ($foo !== $input) {
    // this block is not executed because "array() === array()" => true
    throw new Exception('you have a bug');
}

So: What is the proper way to compare two PHP arrays and make sure, they are different instances (no matter if the content is the same)?

Answer 1

Memory locations refers to pointers. Pointers are not available in PHP. References are not pointers.

Anyway, if you want to check if $b is in fact a reference of $a, this is the closest you can get to an actual answer:

function is_ref_to(&$a, &$b) {
    if (is_object($a) && is_object($b)) {
        return ($a === $b);
    }

    $temp_a = $a;
    $temp_b = $b;

    $key = uniqid('is_ref_to', true);
    $b = $key;

    if ($a === $key) $return = true;
    else $return = false;

    $a = $temp_a;
    $b = $temp_b;
    return $return; 
}

$a = array('foo');
$b = array('foo');
$c = &$a;
$d = $a;

var_dump(is_ref_to($a, $b)); // false
var_dump(is_ref_to($b, $c)); // false
var_dump(is_ref_to($a, $c)); // true
var_dump(is_ref_to($a, $d)); // false
var_dump($a); // is still array('foo')

I hope this solves your problem.

Answer 2

try this function . Arrays are compared like this with standard comparison operators

function standard_array_compare($op1, $op2)
{
    if (count($op1) < count($op2)) {
        return -1; // $op1 < $op2
    } elseif (count($op1) > count($op2)) {
        return 1; // $op1 > $op2
    }
    foreach ($op1 as $key => $val) {
        if (!array_key_exists($key, $op2)) {
            return null; // uncomparable
        } elseif ($val < $op2[$key]) {
            return -1;
        } elseif ($val > $op2[$key]) {
            return 1;
        }
    }
    return 0; // $op1 == $op2
}