--- title: Object-Oriented Principles in PHP kind: note description: 'Link Course notes: Laracasts Learn Laravel Path Object-Oriented Principles in PHP 01 - Classes Think of a class like a blueprint with functionality common to all instances/objects. Nouns make most…' words: 576 readingMinutes: 3 created: '2023-04-08T00:00:00.000Z' updated: '2024-06-12T18:20:49+02:00' website: https://laracasts.com/series/object-oriented-principles-in-php --- ## Link # Course notes: Laracasts > [Learn Laravel Path](https://laracasts.com/path) > [Object-Oriented Principles in PHP](https://laracasts.com/series/object-oriented-principles-in-php) ## [01 - Classes](https://laracasts.com/series/object-oriented-principles-in-php/episodes/1) - Think of a class like a blueprint with functionality common to all instances/objects. - Nouns make most sense as class names. ## [02 - Objects](https://laracasts.com/series/object-oriented-principles-in-php/episodes/2) - The constructor function is called `__construct`. - A public static method is also called a "class method". - The [`...` operator](https://www.php.net/manual/en/migration56.new-features.php) (a.k.a. "splat" in other languages) allows accepting a variable number of arguments, which are accessible as an array. It was introduced in [PHP](/notes/php) 5.6. ## [03 - Inheritance](https://laracasts.com/series/object-oriented-principles-in-php/episodes/3) - The `extends` keyword defines a child class, expressing a "is-a" relationship with the parent class. - Creating a child class is called "subclassing". - The `use` keyword, in addition to being related to namespaces, also has another meaning in [closures](https://wiki.php.net/rfc/closures), making variables from the parent scope visible inside a lambda function. - `array_map` runs a callback against each item of an array, returning a new array. - `array_column` selects a property of each item of an array, returning a new array. - `array_sum` sums all items in a (numeric) array. - `class_basename()` is a [Laravel](/notes/laravel) helper function that returns the name of the actual class (i.e. if a subclass is instantiated, code in the parent class can use this method to know the name of the child class that the object was instantiated from). - Child classes can override parent members which have `public` or `protected` [visibility](https://www.php.net/manual/en/language.oop5.visibility.php). ## [04 - Abstract Classes](https://laracasts.com/series/object-oriented-principles-in-php/episodes/4) - `str_replace` finds and replaces strings within strings. - `preg_replace` uses regular expressions to find and replace patterns in strings. - `strtolower` lowercases a string. - The `abstract` keyword: - makes a class "un-instantiable" (but it can be subclassed) - declares that a method must be implemented in a child class ## [05 - Handshakes and Interfaces](https://laracasts.com/series/object-oriented-principles-in-php/episodes/5) - Being a dynamic language, PHP supports "duck typing": If something walks like a duck and quacks like a duck, it probably is a duck. The disadvantage is that IDEs cannot provide type checking and the code becomes less robust. - The `interface` keyword defines an interface. - Think of an interface as a class without behavior - only method signatures. - The `implements` keyword declares that a class implements an interface. - Think of "duck typing" as a handshake and of interfaces like formal contracts. ## [06 - Encapsulation](https://laracasts.com/series/object-oriented-principles-in-php/episodes/6) - Both methods and properties can have a visibility (public/protected/private) assigned. - The default visibility is public (e.g. `var` and `public` have the same meaning). - Sometimes you have to make something public because it needs to be accessible by another part of your application, even though you don't want to expose the functionality to third-party consumers of your API. In such cases developers often tag (annotate) the methods intended for third parties with `@api` or similar. ## [07 - Object Composition and Abstractions](https://laracasts.com/series/object-oriented-principles-in-php/episodes/7) - Object composition = a class has a reference to an object of another class ## [08 - Value Objects and Mutability](https://laracasts.com/series/object-oriented-principles-in-php/episodes/8) - A value object protects simpler types (e.g., integers, strings, etc.) from being set to values that are invalid in the specific context. - To modify the values in a value object, create a new instance, add methods to make the values mutable, or add methods that return a new instance with the desired values. - Another use case for value objects is to group properties that belong together, such as the x and y of a set of coordinates, or the currency and the numeric value for an amount of money. ## [09 - Exceptions](https://laracasts.com/series/object-oriented-principles-in-php/episodes/9) - If you might reasonably expect some behavior, it shouldn't throw an exception (but e.g. return false instead). - Always protect the state/data at the lowest level. - Create custom Exception subclasses only for important cases where a clear business rule is being broken.