Currently I am trying to create a linked list, which i think is
a data structure composed of nodes where each node stores an item and a pointer to the next node in the data structure.
Here is the class I am using to create nodes:

class node{
    public:
        int item;
        node* ptr_next;
        node(int new_item = 0, node* new_ptr_next = nullptr):
            item(new_item), ptr_next(new_ptr_next){}
};

Here is the function I have used to add nodes to the tree:

//Adds a node to the end of the linked list.
//by making the last node point to the new node
node append_node(const int& item, node* ptr_entry_node){
    node* ptr_last_node;
    node* ptr_current_node;
    //Finds Last Node In List
    ptr_current_node = ptr_entry_node;
    while (ptr_current_node->ptr_next != nullptr){
        ptr_current_node = ptr_current_node->ptr_next;
    }
    ptr_last_node = ptr_current_node;
    //Instanciates a new node and makes the last node point to the new node
    node new_node(item);
    ptr_last_node->ptr_next = &new_node;
    return new_node;
}

Here is the main program.

int main(){
    //Creates a node for the beggining of the linked list.
    node entry_node;
    append_node(12,&entry_node);
    std::cout<<entry_node.item<<"n";
    std::cout<<entry_node.ptr_next->item<<"n";
}

When I run main(), I receive the following output:

0
12

This is the output i expect.
however if i change append_node to:

void append_node(const int& item, node* ptr_entry_node){
        //Exact same code but no "return new_node;"
}

When I run main(), I receive the following output:

0
-1108142424

The second number outputted changes when i run the program again.
This is not what i expect.

I would greatly appreciate your help, if someone could explain why i need to return new_node; in `append_node’, for the new node to be added to the linked list successfully.