A brief discussion on the use of absolute paths and relative paths in php_PHP tutorial

Look at the two pieces of code below:

Code 1: Relative address access

[php]


echo $_SERVER['DOCUMENT_ROOT'];
?>

Code 2: Absolute address access

[php]


echo $_SERVER['DOCUMENT_ROOT'];
?>


Let’s put these two aside for a moment, and let’s talk about the pure html code (ps: now it’s a test, so I’ll write it briefly, but I can get the results)

Code 1: Relative address (test_image_1.html)

[html]

Code 2: Absolute address (test_image_2.html)
[html] view plaincopy

(ps: Picture directory: C:/Program Files/Zend/Apache2/htdocs/1.jpg
          html directory: C:/Program Files/Zend/Apache2/htdocs/test_image/)

Note: Appache is installed on this machine, which is included in Zend’s fusion package.

Two ways, the first is to directly double-click to open the file, both test_image_1 and test_image_2 can be opened, the URL shown is C:/Program Files/Zend/Apache2/htdocs/test_image/test_image_1, so the pictures are all can be displayed.

The second method is to access through appache and use URL: 127.0.0.1/test_image/test_image_1. The result is that the relative path can be implemented normally, but the absolute path cannot be displayed.

After checking a lot of information, I can finally draw a conclusion. Open the html file directly, because under your computer, the absolute path can be easily accessed. But when accessed through WEB, the default root directory of WEB is htdocs/. In your computer, this directory is C:/Program Files/Zend/Apache2/htdocs/. However, WEB does not think so, and it does not know that there is c in its understanding. :This thing. So the absolute path you think is the absolute path in your computer, but this path is not recognized through the WEB.

The correct way should be the following two codes:

Code 1: Relative address (test_image_1.html)

[html]

Relative paths are absolutely fine. Therefore, it is generally recommended to use relative paths to facilitate transplantation.
Code 2: Absolute address (test_image_2.html)
[html] view plaincopy

The following directory here is /, so this is the absolute path.
If you change the location of your picture, the absolute path on your computer is C:/Program Files/Zend/Apache2/htdocs/111/222/333/1.jpg

Then the code should be written as:

[html]

In summary, don’t confuse the absolute path of the computer with the absolute path of the WEB server.
After the above explanation, you should understand the absolute path and relative path in html mode.

So let’s take a look at the form of PHP given at the beginning of the article.

Code 1: Relative address access test_image_1.php
[php]


echo $_SERVER['DOCUMENT_ROOT'];
?>

Code 2: Absolute address access test_image_2.php
[php] view plaincopy


echo $_SERVER['DOCUMENT_ROOT'];
?>

First of all, you need to understand the execution method of PHP. When you access a PHP, it will trigger the PHP to run. After PHP is parsed by appache (the implication is that PHP has finished running and some results are displayed), some HTML code is generated, and To put it simply, the php you have is actually the same as html. PHP is run on the server side and then delivered to you. So I didn't fully understand it at first. Using PHP to do some actions, such as submitting forms, is actually not a PHP thing, but an HTML action. What comes into your hands and can be displayed is the html code with the .php suffix.
Let’s talk about the absolute address in the eyes of PHP. Of course, PHP knows the absolute path of your computer. For example, if you want to use PHP to open a file and use PHP to read the size and resolution of an image on your computer, it is completely fine. Use absolute paths (relative paths are less problematic).

But after PHP is executed, the results will be displayed on your web page, so for example:

[php]

Although this code is written in the PHP file, it is only HMTL code, so it is not just about PHP at this time, but HTML is launched, and HTML is related to WEB, and WEB does not recognize your path (the reason has been mentioned above ). So now it's the WEB that doesn't know the absolute path of the computer, not your PHP that doesn't know it.
 

One thing to mention, the root directory of the WEB is /. However, your pictures are also accessible one level above the root directory it considers. The code is as follows:

[html]
img src="../../1.jpg" />
(Originally, 1.jpg is in the following directory, and the html code is placed under /image_test/, so you need ../1.jpg to access it,
Now 1.jpg is one level above the root directory, then we can access it by going back one level, ../../1.jpg)
Author: wolinxuebin

http://www.bkjia.com/PHPjc/478111.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/478111.htmlTechArticleLook at the two pieces of code below: Code 1: Relative address access [php] meta http-equiv=Content-Typecontent= text/html;charset=GBK ?php echo $_SERVER[DOCUMENT_ROOT]; ? img src=../1.jpg / Code...