Outputting data with JQuery & PHP

I have a general question regarding quality of writing code ...

I'm working on website, that outputs data from MySQL with PHP and it is being called with $.get() / $.ajax() with jQuery....

Now my question is .. the data I´m exporting for example: an array of comments (from class Comments) for a specific post, and this array is being returned from PHP as a string with its HTML manipulation (return '<div id="this->$data"> this->$data</div>';) and with the JQuery manipulation, I´m adding all the comments as list elements or anything else to a specific html element.

Is it useful to do this? Or it is better to send the array in a variable to jQuery, and then work with its elements and make the dynamic html code directly in JavaScript/jQuery..

If that was confusing, is it better to generate the html code in PHP when returning /echoing, or to generate the html code in jQuery after receiving the core data from the 开发者_如何学Cphp?

I know there are other methods like XML JSPN, I'm just asking here about the efficient with generating HTML to manipulate core data (example: Array or Core Json data)

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Let me elaborate on AlberVo's answer

The PHP file which is generating the data, if it is going to be called from possibly other sources, say from an iPhone app, or a command line application or a desktop application, or even if say 2 months down the line you think your website's front-end is going to be say Flash based, then its better to keep your PHP code front-end agnostic and just return xml/json/yaml.

If you know its going to remain a HTML/Javascript based front-end and front-end load speed is an issue, then you can do all the hard work of converting your data into HTML in the PHP file.

In the end personally, I'd say stick to just generating front-end agnostic xml/json/yaml. You never know what direction of the code the future may bring. And architecting your design this way keeps you flexible a.k.a your front-end and middle-tier are loosely coupled.

A few more advantages to such an approach (which really just arise from the loose coupling)

1. Work organization. If in the future someone else is also working on this project one of you can work on the middle-ware and the other on the front-end as long as you respect the json/xml/yaml in between. Your work is not going to affect the other's.

2. Testing. Using a xml/json/yaml also allows you to unit tests your PHP code and front-end easier. Your test data is just xml/json/yaml.

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The way I decide on this is if I foresee using the data for things other than that specific use, then it is better to return the raw data such as json or xml.

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You will want to consider which part of your application should control your page structure and layout. Do you want your page structure to be defined by the PHP script that just returns data? Or do you want to define the page structure in the page itself, and let the PHP script just return the data as needed.

This is an issue addressed by the MVC (Model-View-Controller) pattern. If you follow the MVC pattern, you will separate logic from presentation, rather than mixing the two. This allows your application to remain as flexible as possible, and also promotes code reuse.