array: store multiple values per key

I once trying adding two values with the same key, but it didn't work. It overrode the old value. Isn't it possible to add more than one value with the same key, and when retrieving by key, I get a linked list 开发者_JAVA技巧which I can iterate to get all the different values?

the simplest option: wherever you use $array[$key]=... replace it with $array[$key][]=...

Not unless you actually store an array as the value. Hashtables in PHP map a key to one value. That value could be an array, but you have to build the array yourself. You might consider creating a class to do this for you.

You can create a wrapper function:

function add_to_array($array, $key, $value) {
    if(array_key_exists($key, $array)) {
        if(is_array($array[$key])) {
            $array[$key][] = $value;
        }
        else {
            $array[$key] = array($array[$key], $value);           
        }
    }
    else {
        $array[$key] = array($value);
    }
}

So you just create a 2-dimensional array. You can retrieve the "linked list" (another array) by normal array access $array[$key].

Whether this approach is convenient is up to you.