What are the key differences between PHP_SELF, PATH_INFO, SCRIPT_NAME, and REQUEST_URI?

Understanding PHP_SELF, PATH_INFO, SCRIPT_NAME, and REQUEST_URI**

When developing PHP applications, it's essential to understand the differences between these server variables. Here's a breakdown of their uses:

PHP_SELF

• Normally points to the current script file, e.g. /index.php/faq/whatever
• In CodeIgniter, it's always index.php, as requests are routed to the main controller.

PATH_INFO

• Contains the path information after the script name (not including query parameters), e.g. /faq/whatever
• Useful for accessing specific sections of a URI.

SCRIPT_NAME

• Points to the actual PHP script file being executed, e.g. /test.php
• Unlike PHP_SELF, it doesn't include any path information or query parameters.

REQUEST_URI

• Represents the full request URI, including path information and query parameters, e.g. /test.php?foo=bar
• Useful for determining the complete URL without accessing the server configuration.

Practical Differences

Example 1: PHP_SELF vs SCRIPT_NAME

If the requested URL is in the form /test.php/foo/bar:

• PHP_SELF: /test.php/foo/bar
• SCRIPT_NAME: /test.php

Example 2: REQUEST_URI vs SCRIPT_NAME

If a non-empty query string is entered in the URL:

• SCRIPT_NAME: /test.php
• REQUEST_URI: /test.php?foo=bar

Example 3: REQUEST_URI vs SCRIPT_NAME with Apache Mod Rewrite

With server-side redirection, e.g., /test.php is rewritten to /test2.php:

• REQUEST_URI: /test.php
• SCRIPT_NAME: /test2.php

Example 4: REQUEST_URI vs SCRIPT_NAME with Error Handling

• With Apache mod_rewrite, a 404 error in /test.php might result in:

  • REQUEST_URI: /test.php
  • SCRIPT_NAME: /404error.php

The choice of which server variable to use depends on the specific application requirements. For example, if you need to access path information without query parameters, PATH_INFO would be suitable. If you want the full request URI, REQUEST_URI provides this information.

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