Page 218 - Beginning PHP 5.3

Part II: Learning the Language
The calcMpg() method take two arguments — miles traveled and gallons of fuel used — and
returns the calculated miles per gallon. The method is then tested by calling it with some sample figures
and displaying the result.
Unlike the accelerate() , brake() , and getSpeed() methods you created in the car_simulator.php
example earlier, the calcMpg() method doesn ’ t depend on an actual object to do its job, so it makes
sense for it to be static. Notice that the calling code doesn ’ t need to create a Car object to use calcMpg() .

If you need to access a static method or property, or a class constant, from within a method of the same
class, you can use the same syntax as you would outside the class:
class MyClass {

const MYCONST = 123;
public static $staticVar = 456;

public function myMethod() {
echo “MYCONST = “ . MyClass::MYCONST . “, “;
echo “\$staticVar = “ . MyClass::$staticVar . “ < br / > ”;
}
}

$obj = new MyClass;
$obj- > myMethod(); // Displays “MYCONST = 123, $staticVar = 456”

You can also use the self keyword (much as you use $this with objects):

class Car {

public static function calcMpg( $miles, $gallons ) {
return ( $miles / $gallons );
}

public static function displayMpg( $miles, $gallons ) {
echo “This car’s MPG is: “ . self::calcMpg( $miles, $gallons );
}
}

echo Car::displayMpg( 168, 6 ); // Displays “This car’s MPG is: 28”

Using Hints to Check Method Arguments
Generally speaking, PHP doesn ’ t care much about the types of data that you pass around. This
makes PHP quite flexible, but it can cause problems that are quite hard to track down. Consider the
following code:

class Car {
public $color;
}

class Garage {
public function paint( $car, $color ) {

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