Classes (PHP)

PHP is an object oriented programming language. This article is an introduction to classes and object oriented programming. It's not very PHP-specific.

Classes

In PHP, a "class" is a blueprint or template for creating objects. It defines a set of properties (variables) and methods (functions) that the objects created from the class will have. Classes are a fundamental concept in object-oriented programming (OOP), and they are used to model real-world entities and encapsulate data and behavior related to those entities:

• Objects: Objects are instances of a class. You can create multiple objects from the same class, and each object will have its own set of properties and methods defined by the class
• Properties: Properties (also known as member variables or attributes) are variables associated with a class. They store the data that represents the state of an object. Each object has its own copy of the class's properties
• Methods: Methods are functions defined within a class. They encapsulate the behavior or actions that objects created from the class can perform. Methods can operate on the class's properties and interact with other objects
• Encapsulation: Classes provide a way to encapsulate data and behavior. This means that the internal details of how a class works are hidden from the outside, and access to properties and methods is controlled through visibility modifiers (e.g., public, private, protected)
• Inheritance: PHP supports inheritance, which allows you to create a new class that inherits properties and methods from an existing class. This promotes code reuse and allows you to create specialized classes based on more general ones
• Polymorphism: Polymorphism is the ability to use different classes or objects in a consistent way. In PHP, this is often achieved through interfaces and abstract classes.

Example

###################################################################
# Class definition
###################################################################
#
class Person{
    #
    # Define properties   
    ########################################
    #
    public $name;
    public $age;


    # Define constructor method
    ########################################
    #
    public function __construct($name, $age) {
        $this->name = $name;
        $this->age = $age;
    }


    # Define method "introduce()"
    ########################################
    #
    public function introduce() {
        echo "Hi, I'm {$this->name} and I'm {$this->age} years old.";
    }
}


###################################################################
# Main script
###################################################################
#
#
# Create an object from the class
########################################
#
$person1 = new Person("Alice", 30);


# Call "introduce()" method
########################################
#
# Output: Hi, I'm Alice and I'm 30 years old.
#
$person1->introduce();

Get methods

Example get_class_methods [1]:

$sql="show databases;";
$result = $conn->query($sql);

print_r(get_class_methods($conn));

Get properties

Voorbeeld get_objects_vars [2]:

sql="show databases;";
$result = $conn->query($sql);

print_r(get_object_vars($conn));

See also

• Arrays (PHP)
• wp user list (WP-CLI)

Sources

• https://www.php.net/manual/en/language.oop5.references.php