how to control request with htaccess

Question

# BEGIN 
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END

I am a beginner in htaccess , so does any one help me to describe what is that lines means?

Answer 1

The .htaccess is rewriting all requests except for directories and physical files that exist in the rewrite base (the directory where this .htaccess lives, it looks like) to /index.php. This is a fairly standard practice with many Frameworks and Content Management Systems to achieve the "pretty" URLs (such as you see with Stack Overflow).

You might be interested in the mod_rewrite docs, also.

Answer 2

A little more in detail:

• <IfModule mod_rewrite.c>
  The contents of a <IfModule> block are only processed if the condition is true. In this case the enclosed directives are only processed if the module mod_rewrite is loaded.

• RewriteEngine On
RewriteEngine On is needed to enable the rewriting engine for that directory and its subdirectories.

• RewriteBase /
RewriteBase / sets the per-directory base URL path to /. But this is only necessary if the URL path is not the physical path.

• RewriteCond %{REQUEST_FILENAME} !-f
  This condition states that the requested filename (the requested URL path mapped to the file system) must not be a regular file.

• RewriteCond %{REQUEST_FILENAME} !-d
  The same as the previous but it must not be an existing directory.

• RewriteRule . /index.php [L]
  This rule will match any non empty URL path (more precisely: the requested URL path without the base URL path) and substitutes it with /index.php if the corresponding conditions both are true. Additionally it is flagged as the last rule, so when the rule is applied, the current rule processing will stop here.

• </IfModule>
  Counterpart to <IfModule …>.