Which of the following expressions shows a correct PHP array definition?

a. $products = 'Tires':'Oil':'Spark Plugs';
b. $products = ['Tires', 'Oil', 'Spark Plugs'];
c. $products = ('Tires', 'Oil', 'Spark Plugs');
d. $products = {'Tires', 'Oil', 'Spark Plugs'};

b. $products = ['Tires', 'Oil', 'Spark Plugs'];