Zend框架如何在类外使用$ this？

Question

I am fairly new to OOP in PHP, and I tried to create my own layout class.

In my case, it works like this:

$layout = new Layout('some name'); // title
$layout->setStyle('somestyle.css');
$layout->addDiv('id/class', $content );

Then, just in order to see how professionals create templating applications, I started reading Zend website, the manual part where creation of layouts is covered , but I am failing to understand how is it possible that they have a separate PHP file to initialize the layout, but the layout itself is located in a regular html file.

In that file, they are using $this variable among HTML tags, but how can they do it without triggering 'use of $this variable outside of class context' error? As far as I can see, the tags are not internally included into any class, nor is any PHP file included into the template file.

Could you please provide a simple explanation / example of how this works?

Answer 1

template.php

<p><?php echo $this->foo(); ?></p>

class.php

class Bar {

    public function render() {
        include 'template.php';
    }

    public function foo() {
        return 'foo';
    }

}

$bar = new Bar;
$bar->render();

This is how. The template file is included in a class method.

Answer 2

They're using include() and/or require . Anything that is loaded up via those functions acts as if it was literally cut&pasted into calling code. eg

includeme.php:

<?php
    $var = 'foo';

Some other file:

<?php

function bar() {
   include('includeme.php');
   echo $var;   // ouputs "foo"
}
echo $var; // outputs "PHP Notice: Undefined variable: var

In object code:

includemephp:

<?php
    $this->var = 'foo';
    echo $this->whatever;

And some other file:

class foo {
   public $var;
   public $whatever = 'yoohoo!';

   function bar() {
      include('includeme.php');
      echo $this->var;
   }
}
$x = new foo();
$x->bar(); // outputs `yoohoo!foo`

Since the included text is DIRECTLY inserted into the code at the point include() is called, as if the contents of the included file were literally cut/pasted at that spot, there is no difference for $this inside the included file - it's operating inside that method call, and $this will work as expected.

But if you had a simple file like this:

<?php
    include('includeme.php');

You will get the Using $this when not in object context error, because there is no object/method surrounding the included code.