What is the correct syntax to create an instance of a class that extends another class in PHP?

When creating an instance of a class that extends another class in PHP, you need to use the `new` keyword followed by the name of the child class. The child class will automatically inherit the properties and methods of the parent class. Make sure that the child class properly extends the parent class using the `extends` keyword.

class ParentClass {
    // Parent class properties and methods
}

class ChildClass extends ParentClass {
    // Child class properties and methods
}

// Creating an instance of the child class
$childInstance = new ChildClass();