PHP does not have multidimensional arrays. All arrays are one-dimensional: each pair has a single key and a single value. You can use arrays as such values, nesting arrays inside arrays, but each is still its own value. So every getting at a member of a “multidimensional array” requires accessing multiple arrays: the outer array, and the inner array(s). PHP's arrays are also “pass by value”, which means in this context that every value containing an array is conceptually independent, acting as if PHP is making a copy of it every time you assign it to another variable, property or index. In reality, multiple values can point to the same array, it's just that PHP will make a copy if you try to change it. This latter point means that this code does not change the value of $array['level1']['level2']: $a = $array['level1']; $a['level2'] = 'some_value'; After the first statement, $a points to the same array as $a['level1'] does. However, when the second statement modifies $a, it doesn't any more, because PHP makes a copy of it. Only the copy is modified. This code does change the value, however: $array['level1']['level2'] = 'some_value'; You might imagine that this is equivalent to the previous code. It's not, however, because like in other languages similar to C, the left-hand side of an assignment is sort of magical, and PHP gets to cheat a bit. The closest you can get is to use references, e.g. this does change $array['level1']['level2']: $a = &$array['level1']; $a['level2'] = 'some_value'; It works a little differently internally (in particular, this is very slightly slower), but it has basically the same effect. So, what's up with ArrayAccess and ArrayObject? Well, it turns out that ArrayObject doesn't really use ArrayAccess. ArrayObject is an internal PHP class and so it can use the more powerful internal interface that PHP code isn't able to use. In particular, it has some magic which allows this to work: $array['level1']['level2'] = 'some_value'; Specifically, it enables PHP to grab the array returned by $array['level1'] and modify it in place, without creating a copy. Unfortunately, plain PHP classes are not able to use this magic, so if $array is just a class with public function offsetGet($key) and you try this, you get: PHP Notice: Indirect modification of overloaded element of MyClassImplementingArrayAccess has no effect in Command line code on line 1 offsetGet is returning a value containing an array, and you can change that array, but it won't affect the other values containing that array. However, there is a workaround. If you recall from earlier, you don't have access to PHP's internal magic, but you do have access to references. If you change your implementation to be function &offsetGet($key), so that it returns by reference, $array['level1']['level2'] = 'some_value'; will work. I hope that makes sense. More on reddit.com

$value = $country[$state][$city] ?? null; More on reddit.com

[dim1a] => Array If it were empty, it would be "Array()" Just "Array" indicates to me that the values aren't being displayed Smells like a xdebug issue. Xdebug configured the same? Try var dumping that specific array Maybe need to htmlspecialchars ? I can guarantee you there's no difference in how PHP parses the request and population $_POST. Don't fall down the wrong rabbit hole More on reddit.com

Off the top of my head, it seems you'll have to do the array_keys() and see if it's in there, although there's also array_key_exists(). if the key isn't there, then do foreach() to look at each of those elements'. If there's always exactly nested levels, it's not too bad. If it's a variable number of levels, you'll probably have to use a recursive function. You should also be able to use array_filter() with a custom function. There could be complications, like if more than one entry had that key, or if the key's value is an array. More on reddit.com