Image expire time

The google page speed tool recommends me to set 'Expires' headers fo开发者_运维技巧r images etc. But what is the most efficient way to set an Expires header for an image?

In now redirect all image requests to an imagehandler.php using htaccess:

/*
HTTP/1.1 404 Not Found, HTTP/1.1 400 Bad Request and content type detection stuff
...
*/

header( "Content-Type: " . $content_type );
header( "Cache-Control: public" );
header( "Last-Modified: ".gmdate("D, d M Y H:i:s", filemtime($path))." GMT");
header( "Expires: ". date("r",time() + (60*60*24*30)));
readfile( $path );

But of course this adds extra loading time for my images on first request, and I was wondering if there was a better solution for this.

You can add it in the .htaccess file.

<FilesMatch "\.(ico|jpg|jpeg|png|gif)$">
Header set Cache-Control "max-age=290304000, public"
</FilesMatch>

Found on AskApache.

Of course, if you want the images changed, they won't be downloded again until they expire.

You can solve that by doing something like this

function getImage($path) {
    // may need to add a DOCROOT constant here before filemtime() argument
    return $path . '?m=' . substr(filemtime($path) -5);

}

I just use the substr() to make it a little shorter. The chances of them colliding is minimum, but may happen. Be sure to test it.

Use it like this

<img src="<?php echo getImage('path/to/your/image.jpg'); ?>" alt="" />

http://httpd.apache.org/docs/2.0/mod/mod_expires.html