How Does Doctrine2 Handle Cascade Behavior with ON DELETE CASCADE?

Understanding On Delete Cascade with Doctrine2

Doctrine2 provides the flexibility to configure cascade behavior when working with related entities. However, a common misconception is that setting cascade={"remove"} in the entity association will automatically add the ON DELETE CASCADE option to the foreign key column in the database.

In Doctrine2, there are two distinct types of cascades:

1. ORM-Level Cascade:

• Uses cascade={"remove"} in the entity association.
• A calculation performed by the Unit of Work (UoW).
• Iterates over associated objects and removes them when the parent object is removed.

2. Database-Level Cascade:

• Uses onDelete="CASCADE" on the join column in the entity association.
• Creates the ON DELETE CASCADE option on the foreign key column in the database.

The example provided in the question uses the ORM-level cascade. While it will correctly remove associated child objects when deleting the parent, it does not create the ON DELETE CASCADE option in the database. To achieve this, the following modification is required:

<code class="php">/**
 * @ORM\ManyToOne(targetEntity="Father", cascade={"remove"})
 *
 * @ORM\JoinColumns({
 *   @ORM\JoinColumn(name="father_id", referencedColumnName="id", onDelete="CASCADE")
 * })
 *
 * @var Father
 */
private $father;</code>

It's important to note that using the ORM-level cascade as in the example will result in the removal of the parent object when a child object is removed. This is likely not the intended behavior.

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