Question

I’m wondering if I can write is_numeric($action) someway like this:

switch ($action):
    case NULL:
...

CASE INTEGER: is not working.

Answer 1

I am assuming you want to do a type switch on an input value.

Theoretically you cannot use gettype due to the giant red warning:

Never use gettype() to test for a certain type, since the returned
string may be subject to change in a future version. In addition, it
is slow too, as it involves string comparison.

Instead, use the is_* functions.

Just between you and me, I expect it will work for at least a decade or so. But it makes you feel dirty, it’s true.

In the quest for something officially supported, we might turn to this:

function get_type_stable($var) {
    $types = array('array','integer','double','string','object','resource','null');
    foreach($types as $type) {
        $typechecker = 'is_'.$type;
        if($typechecker($var)) {
            return $type;
        }
    }
}

switch(get_type_stable($var)) {
    case 'integer': // whatever
    case 'null': // etc
}