Archive for January, 2010

By removing the ETag header, you disable caches and browsers from being able to validate files, so they are forced to rely on your Cache-Control and Expires header. Basically you can remove If-Modified-Since and If-None-Match requests and their 304 Not Modified Responses.

Entity tags (ETags) are a mechanism web servers and the browser use to determine whether a component in the browser’s cache matches one on the origin server. Since ETags are typically constructed using attributes that make them unique to a specific server hosting a site, the tags will not match when a browser gets the original component from one server and later tries to validate that component on a different server.

Doing this is simple. First step make sure the Headers mod is enabled:

a2enmod headers

Then, within your apache2.conf file, add the following:

Header unset ETag
FileETag None

You would think a function to remove new lines from a string would exist, but surprisingly it doesn’t. My first thought was to use the nl2br function. nl2br “inserts HTML line breaks before all newlines in a string” and to then strip the br’s out. So something like this:

$string = strip_tags(nl2br($string));

The key word above is “before” though. The function preserves the new lines and just adds a br after it. So I decided to write a function to do it for me:

function removeNewLines($string) {

    $string = str_replace( "\t", ' ', $string );
    $string = str_replace( "\n", ' ', $string );
    $string = str_replace( "\r", ' ', $string );
    $string = str_replace( "\0", ' ', $string );
    $string = str_replace( "\x0B", ' ', $string );

    return $string;

}