Properties and visibility in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the three visibility keywords for properties in PHP classes?

The three visibility keywords are <strong>public</strong>, <strong>protected</strong>, and <strong>private</strong>. They control access to class properties.

beginner

What does a public property mean in PHP?

A public property can be accessed from anywhere: inside the class, in child classes, and from outside the class.

intermediate

Explain the difference between protected and private properties.

<code>Protected</code> properties can be accessed inside the class and by child classes. <code>Private</code> properties can only be accessed inside the class where they are declared.

beginner

How do you declare a private property named $age in a PHP class?

You declare it like this:

private $age;

intermediate

Why is property visibility important in object-oriented programming?

Visibility controls how properties can be accessed, helping to protect data and enforce encapsulation. It prevents unwanted changes from outside the class.

Which visibility keyword allows a property to be accessed only within the class it is declared?

A public

B private

C protected

D static

private properties are accessible only inside the class they are declared in.

If a property is declared as protected, where can it be accessed?

A Inside the class and child classes

B Only inside the class

C Anywhere, including outside the class

D Only outside the class

protected properties are accessible inside the class and by classes that extend it.

What happens if you try to access a private property from outside its class?

A It causes a fatal error

B It works normally

C It returns null

D It triggers a warning but continues

Accessing a private property from outside its class causes a fatal error in PHP.

Which keyword would you use to allow a property to be accessed from anywhere?

A private

B protected

C final

D public

public properties can be accessed from anywhere.

Why might you choose private over public for a property?

A To allow easy access from outside

B To make the property static

C To protect the property from unwanted changes

D To allow access only in child classes

private properties protect data by restricting access to inside the class only.

Describe the three types of property visibility in PHP and give an example of when you might use each.

Think about who should be allowed to see or change the property.

Explain why controlling property visibility is important for maintaining good code structure in PHP classes.

Consider how visibility helps keep code safe and organized.