Lets consider an example. We are creating 2 classes for employees in an office. There are 2 kinds of employees, fulltime and contract employees. Both type of employees have some common methods and properties like, name, monthly salary etc.class EmployeeFulltime { public $fistName = ''; public $lastName = ''; public $annualPay = 0; public function __construct($employee) { $this->firstName = $employee['firstName']; $this->lastName = $employee['lastName']; $this->annualPay = $employee['annualPay']; } public function getFullName() { return $this->firstName . " " . $this->lastName; } public function g...