Apache mod_rewrite
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Mod_rewrite is an Apache module that rewrites browser requests before other modules see them. It uses directives like RewriteEngine, RewriteCond, and RewriteRule that can be placed in the Apache config file or .htaccess files. RewriteCond defines conditions and RewriteRule defines rewrite patterns and substitutions. Mod_rewrite is commonly used to implement "friendly" URLs for search engine optimization and to map old URLs to new URLs after site changes.
![RewriteCond {string} {pattern} [{flags}] {string} is a mod_rewrite variable. Usually, you'll use %{REQUEST_URI}. {pattern} is: An extended regular expression (ereg) A lexical test (>, <, or =) -d (is directory?) -f (is regular file?) -l (is symlink?) other lesser-used values {flags} are NC (“no case”) or OR (“this condition or the next one”)](https://image.slidesharecdn.com/modrewrite-1207193870886494-8/85/Apache-mod_rewrite-6-320.jpg)
![RewriteRule {pattern} {substitution} [{flags}] {pattern} is regular expression to match {substitution} is a string to replace that URL with. It can contain variables, reference parts of the {pattern}, or it can be the special “no substitution” string: - {flags} let you define behavior, like making the browser [R]edirect to the rewritten URL, telling the browser the page is [G]one, or returning a certain MIME [T]ype.](https://image.slidesharecdn.com/modrewrite-1207193870886494-8/85/Apache-mod_rewrite-7-320.jpg)
Apache mod_rewrite
- 1. Apache mod_rewrite Dave Ross The West Suburban Chicago PHP Meetup April 3, 2008
- 2. mod_rewrite is an Apache module that takes what the browser requests and “rewrites” it into something else before the other Apache modules see it
- 3. Request Apache Request mod_rewrite Apache directives Other modules
- 4. mod_rewrite directives can go in the Apache config file (httpd.conf) or in an .htaccess file if I have to put them in httpd.conf, I usually make a separate file and include it Include rewrite_rules.conf
- 5. RewriteEngine on|off RewriteCond RewriteRule The main mod_rewrite directives: They're all you need to get started.
- 6. RewriteCond {string} {pattern} [{flags}] {string} is a mod_rewrite variable. Usually, you'll use %{REQUEST_URI}. {pattern} is: An extended regular expression (ereg) A lexical test (>, <, or =) -d (is directory?) -f (is regular file?) -l (is symlink?) other lesser-used values {flags} are NC (“no case”) or OR (“this condition or the next one”)
- 7. RewriteRule {pattern} {substitution} [{flags}] {pattern} is regular expression to match {substitution} is a string to replace that URL with. It can contain variables, reference parts of the {pattern}, or it can be the special “no substitution” string: - {flags} let you define behavior, like making the browser [R]edirect to the rewritten URL, telling the browser the page is [G]one, or returning a certain MIME [T]ype.
- 8. For a full list of RewriteCond and RewriteRule options, read the docs at: Get really nice “cheat sheets” you can print at:
- 9. mod_rewrite is mostly used to implement “friendly” URLs. They go by many names: Friendly URLs Search Engine Friendly URLs Rational URLs Permalinks
- 10. Search engines like “friendly” URLs. How else are they supposed to know index.php?postid=6 is a different page than index.php?postid=7 ?
- 11. Programs like WordPress and Drupal have support built-in. They'll even write the .htaccess for you. How sweet is that?
- 12. Another common use of mod_rewrite is to map old URLs to new URLs
- 13. Say you change your CMS... Search engines have links, and users have bookmarks to pages in your old CMS. You don't want 404 Not Found errors when they visit those URLs again. So you use mod_rewrite to convert URLs in one format to another
- 14. Need More Info? There's a mod_rewrite tutorial at: This site not only has a tutorial, it has an active message board just about mod_rewrite: