PHP 中静态方法和实例方法的比较

<?php
class MathUtility {
   public static function square($number) {
      return $number * $number;
   }

   public static function cube($number) {
      return $number * $number * $number;
   }
}

// Calling the static methods without creating an instance
$squared = MathUtility::square(5);
$cubed = MathUtility::cube(3);

echo $squared . "<br>"; // Output: 25
echo $cubed; // Output: 27

?>

<?php
class Circle {
   private $radius;

   public function __construct($radius) {
      $this->radius = $radius;
   }

   public function calculateArea() {
      return pi() * $this->radius * $this->radius;
   }

   public function calculateCircumference() {
      return 2 * pi() * $this->radius;
   }
}

// Creating an instance of the Circle class
$circle = new Circle(5);

// Accessing instance methods through the object
echo $circle->calculateArea()."<br>"; // Output: 78.539816339745
echo $circle->calculateCircumference(); // Output: 31.41592653589793
?>

<?php
class MathOperations {
   public static function multiply($a, $b) {
      return $a * $b;
   }

   public function add($a, $b) {
      return $a + $b;
   }
}

// Static method example
echo MathOperations::multiply(5, 2) ."<br>";

// Instance method example
$obj = new MathOperations();
echo $obj->add(3, 4); 
?>