If-Modified-Since

From DreamHost

By querying the If-Modified-Since header, it is possible to build a condition that will return a 304 (Not modified) if the content has not been modified since the client last retrieved a resource. For example, it is possible to use PHP to perform a Conditional GET by examining the value of $_SERVER['HTTP_IF_MODIFIED_SINCE'] and comparing it with a timestamp of the last time the page was modified.

See Also

• HTTP
• Last-Modified
• Conditional GET
• PHP

External Links

• HTTP/1.1 Section 14.25: If-Modified-Since