php＆mysql：在代码之后混淆以确定新对象的属性

Question

I'm a new to coding, and I'm having some trouble understanding a script that sets the new object's properties. Please help me. Thank you in advance.

First, in sign_up.php, I have a input element with POST method as such...

<?php include_once('classes/signup.class.php'); ?>
...
<input type="text" class="input-xlarge" id="name" name="name" 
value="<?php echo $signUp- >getPost('name'); ?>" placeholder="<?php _e('Full name'); ?>">

In the signup.class.php, I have the following code...

class SignUp
function __construct() {
if(!empty($_POST)) {
foreach ($_POST as $field => $value)
$this->settings[$field] = $value;
$this->process();}

public function getPost($var) {
return empty($this->settings[$var]) ? '' : $this->settings[$var];}

}

$signUp = new SignUp();

To my understanding, the getPost($var) will return empty until the form is submitted. Once it is submitted, __constructor() will execute the foreach loop and for the second time, $value will call to parse getPost('name'). This time around, what is $this->settings[$var]?

I am confused, and any of your help will be much appreciated.

Answer 1

Here's your code from classes/signup.class.php (with indentation):

class SignUp {
    function __construct() {
        if (!empty($_POST)) {
            foreach ($_POST as $field => $value) {
                $this->settings[$field] = $value;
            }

            $this->process();
        }
    }

    public function getPost($var) {
        return empty($this->settings[$var]) ? '' : $this->settings[$var];
    }
}

$signUp = new SignUp();

And here's what happens step by step:

1. The code is being evaluated from top to bottom.

2. The first thing that the interpreter evaluates is the definition of your class. So, after encountering class SignUp { ... }, the PHP interpreter will be aware that there is a class called SignUp but it will not execute any part from it yet.

3. Then it encounters the $signUp = new SignUp(); instruction. At this point it instantiates an object of SignUp class and assigns it to the $signUp variable.

4. __construct() is now being evaluated:

   4.1 As $_POST is not empty it will execute the foreach loop.

   4.2 foreach simply iterates over each value from $_POST assigning it to $this->settings.

   Example: assuming that $_POST = array('name' => 'John'), then upon the first iteration (and the only one), $field will become 'name' and $value will become 'John'.

   4.3 Now the interpreter evaluates the $this->settings[$field] = $value; expression which simply translates to $this->settings['name'] = 'John';

   4.4 The foreach loop ends and the $this->process() instruction is now being evaluated.

5. At the end of the execution of classes/signup.class.php in your global namespace there will be an object called $signUp which contains an array member called $settings that consists only of a key ('name') being set to 'John'

6. Now the HTML part of your file is being interpreted and when the interpreter will reach:

   value="<?php echo $signUp->getPost('name'); ?>"

   it will simply evaluate the code inside the PHP tags: echo $signUp->getPost('name');, thus calling the getPost() method on $signUp.

7. The getPost() method simply checkes the $this->settings member (which was previously set - when __constructing the object) and returns the corresponding value for key name (which is 'John').