Title: dynamic cache doesn’t work
Last modified: December 12, 2017

---

# dynamic cache doesn’t work

 *  [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/)
 * Hi!
    I want to use dynamic cash, have made all like was written in fuck instruction
   and nothing help. What I do: 1. Settings->Wp Super cache -> Advance checked this
   chechbox “Enable dynamic caching. (See FAQ or wp-super-cache/plugins/dynamic-
   cache-test.php for example code.)” 2. Than put in my them string ‘kkk’ 3. Added
   this ‘kkk’ in file wp-suer-chache/plugins/dynamic-cash-test.php
 *     ```
       define( 'DYNAMIC_CACHE_TEST_TAG', 'kkk' ); // Change this to a secret placeholder tag
       if ( DYNAMIC_CACHE_TEST_TAG != 'kkk' ) {
       	function dynamic_cache_test_safety( $safety ) {
       		return 1;
       	}
       	add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_cache_test_safety' );
   
       	function dynamic_cache_test_filter( &$cachedata) {
       		return str_replace( DYNAMIC_CACHE_TEST_TAG, "<!-- Hello world at " . date( 'H:i:s' ) . " -->", $cachedata );
       	}
       	add_cacheaction( 'wpsc_cachedata', 'dynamic_cache_test_filter' );
   
       	function dynamic_cache_test_template_tag() {
       		echo DYNAMIC_CACHE_TEST_TAG; // This is the template tag
       	}
   
       	function dynamic_cache_test_init() {
       		add_action( 'wp_footer', 'dynamic_cache_test_template_tag' );
       	}
       	add_cacheaction( 'add_cacheaction', 'dynamic_cache_test_init' );
       }
       ```
   
 * 4. Reload page and I don’t see any changes, What I do wrong?
    This is page [http://kselax.ru](http://kselax.ru),
   in bottom you can see ‘kkk’ doesn’t change, plugin is turned on, cache I removed
   a few times.
 * What the problem and how fix it?

Viewing 6 replies - 1 through 6 (of 6 total)

 *  Thread Starter [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9774652)
 * I changed this line
 *     ```
       define( 'DYNAMIC_CACHE_TEST_TAG', 'kkk' ); // Change this to a secret placeholder tag
       if ( DYNAMIC_CACHE_TEST_TAG != 'kkk' ) {
       ```
   
 * on
 *     ```
       define( 'DYNAMIC_CACHE_TEST_TAG', 'kkk' ); // Change this to a secret placeholder tag
       if ( DYNAMIC_CACHE_TEST_TAG != '' ) {
       ```
   
 * and now I see white screen?
    when off plugin everything works
 *  Thread Starter [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9774706)
 * when I show all errors I didn’t see errors, this is screen [http://prntscr.com/hmfgjz](http://prntscr.com/hmfgjz)
   
   How force this work?
 *  Thread Starter [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9774788)
 * this is file dynamic-test-cache.php
 *     ```
       <?php
   
       /*
        * On the Advanced Settings page enable "Enable dynamic caching" and clear
        * the cache.
        *
        * Plugin authors: NEVER define the template tag for your users. Make them
        * choose one so it will be unique to their site.
        *
        * There are two examples in this file. Both use template tags that must be
        * kept secret.
        *
        * GLOSSARY:
        *
        * Dynamic content: the text or widget you want to show visitors to your site
        * that changes every time it's viewed.
        * Placeholder/template tag: the string of random characters placed in your
        * theme file or printed in an action where the dynamic content will go.
        * Output buffer (ob): any text that is printed by PHP to be sent to the browser
        * but captured by PHP for further manipulation.
        * OB Callback function: A function that is called when the output buffer is
        * filled with a html page. The contents of the page are passed to the function
        * for processing.
        *
        * **** MAKE SURE YOU KEEP THE TEMPLATE TAG SECRET ****
        */
   
       /*
        * EXAMPLE 1
        * http://ocaoimh.ie/2013/10/21/shiny-new-dynamic-content-wp-super-cache/
        * Replace a string in your theme with the dynamic content.
        *
        * dynamic_cache_test_init()
        * This function is the first one to be called. This function hooks
        * dynamic_cache_test_template() to the WordPress action, wp_footer.
        * This script is loaded before WordPress is and the add_action()
        * function isn't defined at this time.
        * This init function hooks onto the cache action "add_cacheaction"
        * that fires after WordPress (and add_action) is loaded.
        *
        *
        * dynamic_cache_test_template_tag()
        * This function hooks on to wp_footer and displays the secret template
        * tag that will be replaced by our dynamic content on each page view.
        *
        *
        * dynamic_cache_test_filter()
        * This function hooks on to the filter through which all the cached data
        * sent to visitors is sent.
        * In this simple example the template tag is replaced by a html comment
        * containing the text "Hello world at " and the current server time.
        * If you want to use the output of a WordPress plugin or command you
        * must enable "late init" on the settings page. Each time you reload
        * the cached page this time will change. View the page source to examine
        * this text.
        *
        * Chronology of a request:
        * 1. dynamic_cache_test_init() hooks dynamic_cache_test_template_tag() on
        *    to the wp_footer action. dynamic_cache_test_filter() is hooked on to
        *    the wpsc_cachedata filter.
        * 2. An output buffer is created by WP Super Cache.
        * 3. Most of the page is generated by WordPress.
        * 4. The wp_footer action fires and the TAG is printed to the page.
        * 5. Processing continues and the page is created.
        * 6. The output buffer finishes. A WP Super Cache callback function runs
        *    and saves the output buffer to a cache file. The wpsc_cachedata 
        *    filter is called.
        * 7. The function dynamic_cache_test_filter() runs and replaces the TAG in
        *    the buffer with the "Hello world" string.
        * 8. The output buffer is pushed to the browser to be displayed.
        */
       error_reporting(E_ALL);
       ini_set('display_errors', TRUE);
       ini_set('display_startup_errors', TRUE);
   
       define( 'DYNAMIC_CACHE_TEST_TAG', 'kkk' ); // Change this to a secret placeholder tag
       if ( DYNAMIC_CACHE_TEST_TAG != '' ) {
       	error_reporting(E_ALL);
       	function dynamic_cache_test_safety( $safety ) {
       		return 1;
       	}
       	add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_cache_test_safety' );
   
       	function dynamic_cache_test_filter( &$cachedata) {
       		return 'hellow';
       		return str_replace( DYNAMIC_CACHE_TEST_TAG, "<!-- Hello world at " . date( 'H:i:s' ) . " -->", $cachedata );
       	}
       	add_cacheaction( 'wpsc_cachedata', 'dynamic_cache_test_filter' );
   
       	function dynamic_cache_test_template_tag() {
       		echo DYNAMIC_CACHE_TEST_TAG; // This is the template tag
       	}
   
       	function dynamic_cache_test_init() {
       		add_action( 'wp_footer', 'dynamic_cache_test_template_tag' );
       	}
       	add_cacheaction( 'add_cacheaction', 'dynamic_cache_test_init' );
       }
   
       /*
        * EXAMPLE 2
        *
        * This is going to be complicated. Hang on!
        *
        * When the cache file for a new page is generated the plugin uses an output
        * buffer to capture the page. A callback function processes the buffer and
        * writes to the cache file. The placeholder tag for any dynamic content has
        * to be written to that cache file but also, it has to be replaced with
        * dynamic content before the page is shown to the user.
        * More on output buffers here: http://php.net/ob_start
        *
        * Unfortunately an extra output buffer is often required when capturing dynamic
        * content such as sidebar widgets. Due to a quirk of the way PHP works it's
        * not possible to have an output buffer run in an output buffer callback. That
        * dynamic content has to be generated before the callback function is reached.
        * The following error occurs when an output buffer is created in the
        * callback function of another output buffer:
        * "PHP Fatal error:  ob_start(): Cannot use output buffering in output buffering display handlers in..."
        *
        * In this example the function add_action() isn't available when this file is
        * loaded so dynamic_output_buffer_init() is hooked on to the "add_cacheaction"
        * cacheaction. That function then hooks dynamic_output_buffer_test() on to the
        * familiar wp_footer action.
        *
        * The first time dynamic_output_buffer_test() runs it generates the dynamic
        * content and captures it with ob_start() in the DYNAMIC_OB_TEXT constant.
        *
        * When the main WP Super Cache output buffer is ready the callback is called.
        * This fires the wpsc_cachedata_safety filter. If the DYNAMIC_OB_TEXT constant
        * is set, which means dynamic content is ready, then it returns 1, a signal
        * that everything is ok.
        * Finally, the wpsc_cachedata filter is run. The function
        * dynamic_output_buffer_test() is hooked on to it. Since DYNAMIC_OB_TEXT is
        * set it replaces the placeholder text with that constant.
        * The resulting html is then sent to the browser.
        *
        * Already cached pages call the safety filter, and then the wpsc_cachedata
        * filter so any hooked function must be ready to generate dynamic content. The
        * very last line of dynamic_output_buffer_test() replaces the placeholder tag
        * with the dynamic content in the cache file.
        *
        *
        * Use an output buffer to capture dynamic content while the page is generated
        * and insert into the right place:
        * Remember to add the DYNAMIC_OUTPUT_BUFFER_TAG text (as defined below) to
        * your theme where the dynamic content should be.
        *
        * dynamic_output_buffer_test() is a function that uses the wpsc_cachedata
        * filter to add a small message and the current server time to every web
        * page. The time increments on every reload.
        *
        */
   
       define( 'DYNAMIC_OUTPUT_BUFFER_TAG', '' ); // Change this to a secret placeholder tag
   
       if ( DYNAMIC_OUTPUT_BUFFER_TAG != '' ) {
       	function dynamic_output_buffer_test( &$cachedata = 0 ) {
       		if ( defined( 'DYNAMIC_OB_TEXT' ) )
       			return str_replace( DYNAMIC_OUTPUT_BUFFER_TAG, DYNAMIC_OB_TEXT, $cachedata );
   
       		ob_start();
       		// call the sidebar function, do something dynamic
       		echo "<p>This is a test. The current time on the server is: " . date( 'H:i:s' ) . "</p>";
       		$text = ob_get_contents();
       		ob_end_clean();
   
       		if ( $cachedata === 0 ) { // called directly from the theme so store the output
       			define( 'DYNAMIC_OB_TEXT', $text );
       		} else // called via the wpsc_cachedata filter. We only get here in cached pages in wp-cache-phase1.php
       			return str_replace( DYNAMIC_OUTPUT_BUFFER_TAG, $text, $cachedata );
   
       	}
       	add_cacheaction( 'wpsc_cachedata', 'dynamic_output_buffer_test' );
   
       	function dynamic_output_buffer_init() {
       		add_action( 'wp_footer', 'dynamic_output_buffer_test' );
       	}
       	add_cacheaction( 'add_cacheaction', 'dynamic_output_buffer_init' );
   
       	function dynamic_output_buffer_test_safety( $safety ) {
       		if ( defined( 'DYNAMIC_OB_TEXT' ) ) // this is set when you call dynamic_output_buffer_test() from the theme
       			return 1; // ready to replace tag with dynamic content.
       		else
       			return 0; // tag cannot be replaced.
       	}
       	add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_output_buffer_test_safety' );
       }
       ?>
       ```
   
 * This is what I get
    [http://prntscr.com/hmfrt6](http://prntscr.com/hmfrt6)
 * As you can see without errors, dynamic-cache doesn’t work?
 *  Thread Starter [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9774889)
 * I’ve found why it didn’t work
    Test code from plugin comes with reference &$cachedata
 *     ```
       function dynamic_cache_test_filter( &$cachedata) {
       		return str_replace( DYNAMIC_CACHE_TEST_TAG, "<!-- Hello world at " . date( 'H:i:s' ) . " -->", $cachedata );
       	}
       ```
   
 * I changed it without $cachedata and start work. Is it normally?
 *  Thread Starter [neo332](https://wordpress.org/support/users/neo332/)
 * (@neo332)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9775006)
 * differences between file that provide with plugin and that is in faq
    [http://prntscr.com/hmglke](http://prntscr.com/hmglke)
 * Is it deliberately did or it’s the occasional error?
    -  This reply was modified 8 years, 5 months ago by [neo332](https://wordpress.org/support/users/neo332/).
 *  Plugin Author [Donncha O Caoimh (a11n)](https://wordpress.org/support/users/donncha/)
 * (@donncha)
 * [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9775297)
 * This [is fixed](https://github.com/Automattic/wp-super-cache/issues/470) in the
   development version which will be released as the next version by the end of 
   the week. You can grab it from the download page at [http://ocaoimh.ie/y/2o](http://ocaoimh.ie/y/2o)
   if you’d like to help test it.

Viewing 6 replies - 1 through 6 (of 6 total)

The topic ‘dynamic cache doesn’t work’ is closed to new replies.

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 * [WP Super Cache](https://wordpress.org/plugins/wp-super-cache/)
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 * 6 replies
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 * Last reply from: [Donncha O Caoimh (a11n)](https://wordpress.org/support/users/donncha/)
 * Last activity: [8 years, 5 months ago](https://wordpress.org/support/topic/dynamic-cache-doesnt-work/#post-9775297)
 * Status: not resolved