Injecting PHP Variables into HTML Code

Not really sure what you are asking, but here is my answer

I don't know the structure of your code, but I hope you are using a MVC approach (or at least something which deals with classes) so that you can do the following:

In your main controller, you create a class variable like viewData which will be an array. And you put in it everything you want

$this->viewData['username'] = $username;
$this->viewData['myArray'] = array('foo' => 'bar');
$this->viewData['menuSubview'] = 'path_to_menu_subview.php';

Then, you create a render function.

public function render()
{
    extract($this->viewData);
    ob_start();
    include("myfile.php");
    return ob_get_clean();
}

And in myfile.php (with the HTML) you can simply do what you used so far

<div id="menu"><?php include($menuSubview);?></div>
<p><?=$username;?></p>
<p><?=$myArray['foo'];?></p>

The whole code can be something like this.

class Something {

    protected $viewData;
    protected $viewFile;

    public function logic()
    {
        $this->userProfile();
        echo $this->render();
    }

    public function userProfile()
    {
        $this->viewData['username'] = 'John The Ripper';
        $this->viewFile = 'myFile.php';
    }

    public function render()
    {
        extract($this->viewData);
        ob_start();
        include($this->viewFile);
        return ob_get_clean();
    }
}

Here's a simplified class that stores data and allows for recursive rendering of files that all have access to the save data form the initial instance.

class View {

    // view data 
    protected $_data = [];

    /**
     * Set view data 
     */
    public function __set( $key, $value )
    {
        $this->_data[ $key ] = $value; 
    }

    /**
     * Get view data 
     */
    public function __get( $key )
    {
        if( array_key_exists( $key, $this->_data ) )
        {
            return $this->_data[ $key ];
        }
        return null;
    }

    /**
     * Render view file 
     */
    public function render( $file )
    {
        if( is_file( $file ) )
        {
            $view = $this; 
            ob_start();
            include( $file );
            return ob_get_clean();
        }
        return 'File not found: '.$file;
    }
}

Just use the variable $view inside your included files to access the data in the class, or render() another partial file that can do the same thing, and so on.

// Bootstrap a View instance and add some data 
$view = new View; 
$view->dataOne = 'valueOne'; 
$view->dataTwo = 'valueTwo'; 

// Render main template 
echo $view->render( 'template.php' );

Inside template.php

<header>
    <?= $view->render( 'header.php' )  ?> 
</header>

<h1><?= $view->dataOne ?></h1> 
<p><?= $view->dataTwo ?></p>

Nothing is wrong with your injectVariables() function, it is in fact a good idea.

• You shouldn't have performance impact anyway (If this is your main concern your are doing premature optimization !)

• Your view (HTML) shouldn't know about the internal of your application. (You split responsability - this is a huge subject that I won't talk deep) You know if something end-up into $variables it has been build/formatted or is revelent to be display for $filePath.
  In complex system you may end up with a variable with a pdf generator, why would the HTML want that? The only purpose of the HTML is to DISPLAY HTML data.

  Some variables from your logic will end-up in $variables almost every time such as session informations (Who is currently logged), for your case this is normal.

  In the perfect world if you put a class into $variables it should be designed only for purpose of your HTML even if it is almost the same object as your logic.
  As an exemple I designed a Session class in my logic. It does have method such as Logout() and EnsureIsAlive() as well as field such as FullName. FullName is going to be use by my HTML because I want to display it in the header of my page.
  I should have a Session class for the HTML that only contains a FullName field because the HTML has only one job and is it to display data. Login() and EnsureIsAlive() are specific for the logic and aren't related at all with displaying data. In reallity time is always a constraint and because you are writing all by yurself from scratch you may end-up just sending the logic Session class into $variables.

  • Design note : I'm a C# programmer and we always use class over array to pass parameters as a good pratice and it does affect the exemple about how to pass FullName to your HTML. In your case, instead of creating a class dedicated for the HTML you could also create a simple array :

    $variables['Session'] = array('FullName' => $mySession->fullName).
    

  That way you still avoid your HTML to have access to the unrelated method specific for your logic. I'm not sure if it is a good pratice in php...

• Keep context variables clean
  If you do call injectVariables() more than once (for different $PathFile) you may not want the same variables.
  One injectionVariables() could be for a widget, another for a complete complete page.
  Why would a TimeWidget need your totalInvoice variable?

  You also have the ability to prepare multiples $variables at the same time because each injectVariables() will have his own parameters.

I'm not up-to-date but I know phpBB template system use (back near 2000) the exact same pattern as your injectVariables()).

You wrote that each of your page do call injectVariables(), you could also (but it may be complex) do it only in one file - like php frameworks.

Framework handle HTTP requests into one specific file
(eg. http://yoursite.com/hello/world or http://yoursite.com/login would call (internaly) http://yoursite.com/index.php?page=hello&subpage=world and http://yoursite.com?page=login).
Then this page (index.php in my exemple) would include a specific file (controller) according with his GET parameters ($_GET['page'] and $_GET['subpage']).
The controller job would be to fetch data, apply logic then fill $variables.
Then index.php will call injectVariables() with the releated HTML.