我如何将逻辑与演示分开？

然后重复所有数据库或其他服务交互的所有步骤。您的目标是准备好业务逻辑必须提供的所有数据。然后您的业务逻辑结束，您可以转向演示。

如果您可以轻松地交换模板引擎，您可以与坏的分离开来（您无法使用其他方法回答，介意你） - 所以，特定的引擎并不重要。我们来看一个最简单的例子 - PHP

创建一个名为 tpl.php 的文件并将该代码放在

然后将此文件包含在您的业务逻辑文件中。或者 - 更好 - 在更高层次的模板中。

您可以在这个主题 使用这样的分隔，你可以：

尽管从目前的方法或其他方法来看，这一切都是不可能的。这个想法是分离。

Normally I am developing website and coding PHP and HTML something like this -

But recently I came across to know one of my friend, that is a bad practice of saving the HTML in a PHP variable. And also said I need to separate logic from presentation.

If it is true, can anybody tell me how can I do it?

Any comments would be greatly appreciated. Thank you.

How I separate logic from presentation?

Separate it.

Though it is called business logic from presentation logic separation. You have logic in both layers. The name says it all:

• perform your "logic" first
• then turn to "presentation."

Taking your example it have to be something like this

though I would use some more intelligent approach to get data from database, something like this:

then repeat all the steps for all the database or other other services interaction. Your goal is to have all the data ready that business logic have to supply. Then your business logic ended and you can turn to presentation.

You can tell a good separation from the bad one if you can easily interchange template engines (you can't do it with approach from other answer, mind you) - so, particular engine doesn't matter. Let's take a simplest one - PHP

Create a file called tpl.php and put this code there

then include this file in your business logic file. Or - better - in some higher level template.

You can see a good real life example of the approach in this topic

Using such a separation, you can:

While all this is just impossible with your current approach or approach from other answer. The idea is separation of matters.