What is the best practice to use when using PHP and HTML?

I have been designing websites for a while now, but there is one thing that I have never been quite sure of when using PHP and HTML. Is it better to have the whole document in PHP and echo HTML like so:

<?php
  doSomething();
  echo "<div id=\"some_div\">Content</div>";
?>

Or have a HTML file like so and just add in the PHP:

<html>
<body>
  <?php doSomething(); ?>
  <div id="some_div">Content</div>
</body>
</html>

It seems tidier to echo HTML, especially if lots of PHP gets used throughout the page, but doing so loses all formatting of the HTML i.e. colors in the IDE etc.

Solution 1:

There are varying opinions on this. I think there are two good ways:

Use a templating engine like Smarty that completely separates code and presentation.
Use your second example, but when mixing PHP into HTML, only output variables. Do all the code logic in one block before outputting anything, or a separate file. Like so:
```
<?php $content = doSomething();
   // complex calculations
?>
<html>
<body>
  <?php echo $content; ?>       
  <div id="some_div">Content</div>
</body>
</html>
```

Most full-fledged application frameworks bring their own styles of doing this; in that case, it's usually best to follow the style provided.

Solution 2:

I think this would depend on your group's or your own decided convention. And it can and should vary depending on what type of file you're working in. If you follow the MVC pattern then your views should be the latter. If you're writing a class or some non-output script/code then you should use the former.

Try to keep a separation of display or formatting of output and the logic that provides the data. For instance let's say you need to make a quick page that runs a simple query and outputs some data. In this case (where there is no other existing infrastructure or framework) you could place the logic in an include or in the top or the bottom of the file. Example:

<?php
  # define some functions here that provide data in a raw format
?>
<html>
<body>
  <?php foreach($foo = data_function($some_parameter) as $key => $value): ?>
  <p>
    <?=$value;?>
  </p>
  <?php endforeach; ?>
</body>
</html>

Or you could place the logic and function definitions in an include file or at the bottom of the file.

Now if you're producing some sort of class that has output (it really shouldn't) then you would echo the HTML or return it from the method being called. Preferably return it so that it can be output whenever and however the implementer would like.

Solution 3:

The syntax highlighting is an important benefit of the second method, as you said. But also, if you're following good practices where logic and presentation are separated, you will naturally find that your files that contain HTML are almost entirely HTML, which then, naturally, leads to your second method again. This is the standard for MVC frameworks and the like. You'll have a bunch of files that are all PHP, doing logic, and then when that's done they'll include a presentation file which is mostly HTML with a sprinkling of PHP.

Solution 4:

Simple:

More PHP - close HTML in PHP. When you generate HTML code in PHP, when you are doing something like a class, so it is better to make it in echo.

Less PHP - close PHP in HTML. This is stuff like just putting vars into fields of HTML stuff, like forms... And such.

Solution 5:

The best approach is to separate the HTML from the PHP using template system or at least some kind of HTML skeleton like:

<main>
    <header/>
    <top-nav/>
    <left-col>
        <body />
    </left-col>
    <right-col />
    <footer/>
</main>

Each node represents a template file e.g. main.php, hrader.php and so on. Than you have to separate the PHP code from the templates as something like functions.php and fineally use your second approach for template files and keeping functions clean of "echos" and HTML.