How to code properties

      [ public | protected | private ] $propertyName [ = initialValue ];

A private property

      private $firstName;

A public property with a default value

      public $comment = '';

A protected property

      protected $counter;

Five properties on the same line

      private $category, $id, $name, $description, $price;

Description

A public property can be directly accessed by code outside of the class.
Private and protected properties can’t be directly accessed by code outside the class.
By default, properties are public. As a result, if you omit the access modifier, the property is public.
To code an initial value for a property, you must supply a scalar value, an array of scalar values, or NULL. A scalar value is a literal number, string, or Boolean value.
To code multiple properties on the same line, you can separate the property name