Understanding the @ManyToMany annotation with tags

Tags group posts by topics. A tag contains several posts, and a post has several tags. This is a Many-To-Many bidirectional association. Doctrine manages transparently the association table needed to store Many-To-Many relations at the SQL level. The MySQL schema that will be generated is shown in the following screenshot:

Creating the Tag entity class (inverse side)

The Tag entity class has only two properties:

• name: This is the name of the tag, it is unique, and is the identifier of the entity

• posts: This is the collection of posts associated with this tag

The following are the steps to create the Tag entity class:

1. Create a Tag.php file in the src/Blog/Entity/ location that contains the entity class using the following code snippet:

   <?php
   
   namespace Blog\Entity;
   
   use Doctrine\Common\Collections\ArrayCollection;
   use Doctrine\ORM\Mapping\Entity;
   use Doctrine\ORM\Mapping\Column;
   use Doctrine\ORM\Mapping\Id;
   use Doctrine\ORM\Mapping\ManyToMany...