How to model many to many relationships without circles - database

Question

Note: Because my original question wasn't understood clearly I'm writing it completely new!
I have two tables in my database, plus a junction/join table:
Recipes:
CREATE TABLE Recipes(
id INT(11) NOT NULL AUTO_INCREMENT,
name VARCHAR(100) NOT NULL,
PRIMARY KEY (id)
)
Ingredients:
CREATE TABLE Ingredients(
id INT(11) NOT NULL AUTO_INCREMENT,
name VARCHAR(100) NOT NULL,
PRIMARY KEY (id)
)
IngredientsRecipes:
CREATE TABLE IngredientsRecipes(
id INT(11) NOT NULL AUTO_INCREMENT,
recipeId INT(11) NOT NULL,
ingredientId INT(11) NOT NULL,
PRIMARY KEY (id)
)
My Ingredient class in php code looks like this:
class Ingredient{
private $id;
private $name;
private $recipes; //In which recipes this ingredient is used
}
And this is my Recipes class:
class Recipe{
private $id;
private $name;
private $ingredients; //Ingredients used in this Recipe
}
Now when I want to populate the two lists I have the follwing problem:
The Recipe class has many Ingredients, and the Ingredients class has many Recipes. Each class contains contains the other, I hope this litte picture can illustrate the situation.
Recipe | Ingredients | Recipes using |
|used in Recipe | this Ingredient |
----------------+---------------+-----------------+
|--Noodles------|Spaghetti
|
Spaghetti-------|--Sauce--------|--Spaghetti
|
|--Cheese-------|--Spaghetti
|
|--Mac n Cheese
|--Macaroni-----|Mac n Cheese
|
Mac n Cheese----|--Cheese-------|--Spaghetti
|
|--Mac n Cheese
What is the prefered way of writing the model class for a many to many relationship?

Answer 1

This is usually done by a join or mapping table to hold the relationship between the two, e.g.:
CREATE TABLE recipe (
recipe_id NUMERIC PRIMARY KEY
recipe_name VARCHAR (100)
-- etc...
);
CREATE TABLE ingredient (
ingredient_id NUMERIC PRIMARY KEY
ingredient_name VARCHAR (10),
-- etc...
);
CREATE TABLE recipe_ingredient (
recipe_id NUMERIC REFERENCES recipe (recipe_id),
ingredient_id NUMERIC REFERENCES ingredient (ingredient_id),
PRIMARY KEY (recipe_id, ingredient_id)
);