In CakePHP, the belongsTo association is used to define a one-to-many relationship between two models. For example, if you have a Users model and a Posts model, and each post belongs to a user, you can use the belongsTo association to define this relationship.

To define a belongsTo association in a CakePHP model, you will need to use the $belongsTo property. For example:

class Post extends AppModel {
  public $belongsTo = [
    'User' => [
      'className' => 'User',
      'foreignKey' => 'user_id'
    ]
  ];
}

In this example, the Post model has a belongsTo association with the User model. The className option specifies the name of the model being associated with, and the foreignKey option specifies the field in the posts table that stores the associated user’s ID.

You can then use the Post model’s User association to access a post’s user. For example:

$post = $this->Post->findById(1);
$user = $post->user;

This will retrieve the user associated with the post with ID 1.

Note: The belongsTo association is just one of several types of associations available in CakePHP. Other types of associations include hasOne, hasMany, and hasAndBelongsToMany. You can use these associations to define the relationships between your application’s models.