Скачать или смотреть Understanding PHP Inheritance: Does plain_flour Inherit the calories Attribute?

Dive into PHP inheritance and learn how to access inherited attributes. Discover with a practical example whether `plain_flour` has access to the `calories` data.
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This video is based on the question https://stackoverflow.com/q/63081702/ asked by the user 'James' ( https://stackoverflow.com/u/10372932/ ) and on the answer https://stackoverflow.com/a/63081808/ provided by the user 'Fobos' ( https://stackoverflow.com/u/10026757/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding PHP Inheritance: Does plain_flour Inherit the calories Attribute?

When working with object-oriented programming in PHP, understanding how inheritance functions is crucial. A common question many developers face revolves around whether a child class can access attributes and methods of its parent class. Let's explore this concept with a specific example: Does plain_flour have the calories attribute initialized?

The Code Breakdown

Initial Structure

Consider the following PHP code:

[[See Video to Reveal this Text or Code Snippet]]

The Question

You might wonder: Can plain_flour, an instance of the flour class, access the calories attribute defined in the ingredient class, and thus successfully call get_calories()?

Understanding the Problem

Private Attributes in PHP

In the example above, the $calories variable is marked as private in the ingredient class. This means it can only be accessed directly within the same class. Thus, instances of subclasses such as flour cannot directly access the private attributes of their parent classes.

The Solution: Constructor Inheritance

To ensure that plain_flour can use the get_calories() method and access the calories attribute, you need to invoke the parent's constructor in the child's constructor. Here's how you can achieve that:

Revised Code Example

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Explained

Calling Parent’s Constructor: Within the flour class constructor, you include parent::__construct(); This line calls the ingredient constructor, ensuring that the $calories attribute gets initialized.

Accessing get_calories(): Now, you can call $plain_flour->get_calories();, which will return 100, confirming that the calories attribute is correctly inherited and initialized.

Conclusion

To sum up, in PHP, when working with inheritance, it’s important to remember:

Private attributes cannot be accessed directly by child classes.

You must call the parent's constructor to ensure any necessary initialization of attributes happens for child class instances.

By implementing these simple solutions, you can effortlessly leverage the full potential of PHP's object-oriented features. Happy coding!