Stephane Boisvert

For us, (and your milage may vary) We had to switch from APC cache to disk cache for object caching to solve the problem. (even thought one would think this would have something to do with Disk caching).

Are you using APC object caching by any chance? we did and had this problem, we needed to disable it (switch to disk based object caching) for it to work

we have these functions in a file in the plugins folder of w3 total cache plugin.

what they do is make different versions of the page cache based on which browser comes to the site. (for us its IE and everyone else)

If you want to modify the code for it to do store different versions for mobile browsers only it shouldn’t be that hard. But I can’t offer more help than this.

/**
 * Makes different page cache keys based on user agent
 *
 */
function liberal_w3tc_pgcache_cache_key($key){
    global $is_IE, $is_lynx, $is_gecko, $is_winIE, $is_macIE, $is_opera, $is_NS4, $is_safari, $is_chrome, $is_iphone;

    liberal_w3_detect_browser();

    $postfix = "";
    if($is_winIE) {
        $postfix = "winIE";
    }

    if($postfix) $key .= "_" . $postfix;

    return $key;
}
w3tc_add_action('w3tc_pgcache_cache_key', 'liberal_w3tc_pgcache_cache_key');

/**
 * Simple browser detection
 * This code is copied from wp-includes/vars.php because we need it for W3 total cache which is loaded before wp-includes/vars.php
 *
 * @see wp-includes/vars.php:37
 */
function liberal_w3_detect_browser() {
    global $is_lynx, $is_gecko, $is_winIE, $is_macIE, $is_opera, $is_NS4, $is_safari, $is_chrome, $is_iphone, $is_IE;
    $is_lynx = $is_gecko = $is_winIE = $is_macIE = $is_opera = $is_NS4 = $is_safari = $is_chrome = $is_iphone = false;

    if ( isset($_SERVER['HTTP_USER_AGENT']) ) {
        if ( strpos($_SERVER['HTTP_USER_AGENT'], 'Lynx') !== false ) {
            $is_lynx = true;
        } elseif ( stripos($_SERVER['HTTP_USER_AGENT'], 'chrome') !== false ) {
            $is_chrome = true;
        } elseif ( stripos($_SERVER['HTTP_USER_AGENT'], 'safari') !== false ) {
            $is_safari = true;
        } elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'Gecko') !== false ) {
            $is_gecko = true;
        } elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE') !== false && strpos($_SERVER['HTTP_USER_AGENT'], 'Win') !== false ) {
            $is_winIE = true;
        } elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE') !== false && strpos($_SERVER['HTTP_USER_AGENT'], 'Mac') !== false ) {
            $is_macIE = true;
        } elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'Opera') !== false ) {
            $is_opera = true;
        } elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'Nav') !== false && strpos($_SERVER['HTTP_USER_AGENT'], 'Mozilla/4.') !== false ) {
            $is_NS4 = true;
        }
    }

    if ( $is_safari && stripos($_SERVER['HTTP_USER_AGENT'], 'mobile') !== false )
        $is_iphone = true;

    $is_IE = ( $is_macIE || $is_winIE );
}