Yii2 - migration foreign key

A FOREIGN KEY is a key used to link two tables together.
Syntax
    
        $this->addForeignKey(name, table, column, referringTable, referringColumn, delete, update);
        // delete options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
        // update options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
    
Add foreign key
    
        public function safeUp()
        {
            $this->createTable('book', [
                'id' => $this->primaryKey(),
                'name' => $this->string(255)->notNull(),
                'categoryId' => $this->integer(11)->notNull(),
                'price' => $this->integer(11)->notNull(),
                'status' => $this->integer(1)->notNull(),
            ]);

            $this->addForeignKey('fk-categoryId', 'book', 'categoryId', 'category', 'id', 'RESTRICT', 'RESTRICT');
        }
    
Drop foreign key
    
        $this->dropForeignKey('fk-categoryId', 'book');