在PHP中选择WP_Post对象值（如果有）

I have this example array/object:

//$monday array values
Array (
[menu_item1] => 
[menu_item2] =>
Array (
[0] =>
WP_Post Object (
[ID] => 530 
[post_content] => Food selection 2 
[post_title] => Food 2 ) ) 

I'm beginner in WP_Post Objects. How can I get the menu_item1 ID (if it has value) and menu_item2 ID value (if it has too)?

The documentation isn't helped me.

I'm sure it's something like but it doesn't work:

foreach ($monday as $key => $value) {
    if ($value) {
        $myid = $value->ID;
    }
}

From comments( @Erwin ).

foreach ($monday as $key => $value) {
    if ($value) {
        $myid = $value[0]->ID; // this way you can access to object and get id
    }
}

Checking:

foreach ($monday as $key => $value) {
    if (!empty($value)) { //checking all values to not be empty
        if(!empty($value[0])){ //checking, if exists something where you have id
            $myid = $value[0]->ID;
        }
    }
}

Also, you can double check in second statement to get only objects:

foreach ($monday as $key => $value) {
    if (!empty($value)) { 
        if(!empty($value[0]) && is_object($value[0])){ 
            $myid = $value[0]->ID;
        }
    }
}

Also, remember. If sort of your array will changed, then the code above will not gave you result as expected.