For example, the example in symfony2:
Ens\JobeetBundle\Entity\CategoryAffiliate: type: entity table: category_affiliate id: id: type: integer generator: { strategy: AUTO } manyToOne: category: targetEntity: Category inversedBy: category_affiliates joinColumn: name: category_id referencedColumnName: id affiliate: targetEntity: Affiliate inversedBy: category_affiliates joinColumn: name: affiliate_id referencedColumnName: id
A more detailed explanation such as the generator option, and the documentation for manyToOne and OneToMany options
I am not very clear about the doctrine official website