理解PHP类OOP结构[关闭]

Question

I'm trying to create a class function but somehow it won’t work and I can’t figure out what’s the problem. Is it the way I declare the variable or what so ever?

<?php 

class Car{

var $model;
var $make;
var $speed;

function Car ( $model, $make, $speed)
{
    $this->model = $model;
    $this->make = $make;
    $this->speed = $speed;
}

function accelerate ($speed)
{
    $add = 5;
    $speed = $speed + $add;
    return $speed;
}

function get_status()
{
    echo "Car status :   
";
    echo "Model      :"  $this-> model "
";
    echo "Make       :"  $this-> make  "

";
}

function get_speed()
{
    return $this->speed;
}
}
?>

<?php
$car1 = new Car();

$car1 -> get_status("Vios", "Toyota");
for( $i = 0; $i < 5 ; $i++)
{
    echo "Accelerating... <br> 
";
    echo "Current speed : accelerate(5) km/h <br>";
}
?>

Answer 1

Lots of issues with your code. But at least this cleaned up version should work without the script dying completely. Here is a breakdown of what I did:

• Set the variables that were set as var to public since that is the preferred method of setting variables.
• In function Car, I set default values for $model, $make & $speed so if they are not passed—like in your example—there is at least a default value to act on.
• Your echo lines in get_status did not have the . for concatenation so they were not properly concatenating the strings.
• Then you setting $this-> make and $this-> model with empty spaces is syntactically incorrect. So set those to $this->make and $this->model.
• Then when you are calling the class, you set this "Current speed : accelerate(5) km/h <br>"; which is syntactically incorrect as well. So set that to echo "Current speed : " . $car1->accelerate(5) . " km/h <br>"; so it can actually echo values.

But that said, unclear on what the output is for this code. The logic is a bit of a mess. But at least it’s not completely dying like it did before!

And here is the cleaned up code:

class Car {

  public $model;
  public $make;
  public $speed;

  function Car ($model = 0, $make = 0, $speed = 0) {
    $this->model = $model;
    $this->make = $make;
    $this->speed = $speed;
  }

  function accelerate ($speed) {
    $add = 5;
    $speed = $speed + $add;
    return $speed;
  }

  function get_status () {
    echo "Car status :   
";
    echo "Model      :" . $this->model . "
";
    echo "Make       :" . $this->make  . "

";
  }

  function get_speed () {
    return $this->speed;
  }

}

$car1 = new Car();
$car1->get_status("Vios", "Toyota");

for( $i = 0; $i < 5 ; $i++) {
    echo "Accelerating... <br> 
";
    echo "Current speed : " . $car1->accelerate(5) . " km/h <br>";
}

And—like I said before—since the way you are calling the class makes little sense to the structure you have, I slightly reworked the code above so it loops through an array of car values like this:

$car_array = array("Vios", "Toyota");

foreach ($car_array as $car_value) {
  $car1 = new Car($car_value);
  $car1->get_status();

  for( $i = 0; $i < 5 ; $i++) {
    echo "Accelerating... <br> 
";
    echo "Current speed : " . $car1->accelerate(5) . " km/h <br>";
  }
}