Baselibs

Foreign keys ​

Foreign keys are used to create a relationship between two tables.

The Schema class allows you to define foreign keys using the foreign_key() method. This method creates a new Foreign_Key object and adds it to the $foreign_keys array in the Schema class.

Defining foreign keys ​

You can define a foreign key on a column by calling the foreign_key() method on the Schema object.

php
$schema = new Schema( 'my_table', function ( Schema $table ) {
	$table->foreign_key( 'user_id' )
		->reference( 'users', 'id' )
		->on_delete( 'CASCADE' )
		->on_update( 'CASCADE' );
});

Fluent interface ​

The Foreign_Key class uses a fluent interface, allowing method chaining for easy configuration.

You can customize various aspects of the foreign key:

  • Set the reference table and column using reference()
  • Set just the reference table using reference_table()
  • Set just the reference column using reference_column()
  • Set the ON DELETE action using on_delete()
  • Set the ON UPDATE action using on_update()

The reference() method is a key part of defining a foreign key relationship. This method sets both the referenced table and the referenced column in a single call. It's a convenient way to specify the "target" of the foreign key relationship.

Parameters ​

  • $reference_table: The name of the table that this foreign key is referencing.
  • $reference_column: The name of the column in the referenced table that this foreign key is pointing to.

Default values ​

If not specified, the ON DELETE and ON UPDATE actions default to 'NO ACTION'.