Title: Fatal error trying using dynamic content Last modified: August 22, 2016 --- # Fatal error trying using dynamic content * [stebcom](https://wordpress.org/support/users/stebcom/) * (@stebcom) * [11 years, 8 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/) * I’m trying to use dynamic content, as explained in this post: [http://ocaoimh.ie/y/6j](http://ocaoimh.ie/y/6j) * I defined the cache tag * `define( 'DYNAMIC_CACHE_TEST_TAG', 'my-placeholder-string' );` * and put this markup in my template (I need the cart widget not to be cached) * ` * Now I get this error: PHP Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0 * If I delete the DYNAMIC_CACHE_TEST_TAG, then the site works again. * I’m using PHP cache, with dynamic cache and lazy loading options enabled. * What am I doing wrong? * [https://wordpress.org/plugins/wp-super-cache/](https://wordpress.org/plugins/wp-super-cache/) Viewing 8 replies - 1 through 8 (of 8 total) * Thread Starter [stebcom](https://wordpress.org/support/users/stebcom/) * (@stebcom) * [11 years, 8 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5244677) * I forgot to replace * `add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_output_buffer_test_safety');` * with * `add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_cache_test_safety' );` * but I’m not able to get things working: I simply don’t see the code replacement. * Thread Starter [stebcom](https://wordpress.org/support/users/stebcom/) * (@stebcom) * [11 years, 8 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5244906) * Ok, * now I figured out how to make the dynamic cache work, but I have another problem now: I’m using the output buffer but it’s working only with Google Chrome, as the string replacement is not being performed with IE, nor Firefox. Unfortunately, I can’t spot any error and the cache logs the same lines after a page request made by Chrome and a page request made by Firefox or IE. * Any idea about this? * [0utf1t](https://wordpress.org/support/users/0utf1t/) * (@0utf1t) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245055) * Hey! I have the same problem! How did you get working? In pagesource I see Hello world with time… but if I do this * The date still gets cached. Please tell how did you get to work! I’m search for solution a week now! * Thread Starter [stebcom](https://wordpress.org/support/users/stebcom/) * (@stebcom) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245056) * This is an example of usage for a woocommerce cart widget. I use this code in functions.php: * ``` if ( DYNAMIC_OUTPUT_BUFFER_TAG != '' ) { function dynamic_output_buffer_minicart( &$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 woocommerce_mini_cart(); $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 ); } function dynamic_output_buffer_init() { add_action( 'wp_footer', 'dynamic_output_buffer_minicart' ); //add_action( 'wp_footer', 'dynamic_output_buffer_sidebar' ); } 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', 'dynamic_output_buffer_minicart' ); add_cacheaction( 'add_cacheaction', 'dynamic_output_buffer_init' ); add_cacheaction( 'wpsc_cachedata_safety', 'dynamic_output_buffer_test_safety' ); } ``` * And this code in my template page: * ``` Loading cart... ``` * You should also enable late_init option in the WP Super Cache configuration. * [0utf1t](https://wordpress.org/support/users/0utf1t/) * (@0utf1t) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245057) * Thanks a lot for reply. Did you also managed to get working the first way with‘ DYNAMIC_CACHE_TEST_TAG’ ? * Yes late_init is enable, dynamic cache is enabled in php caching mode. * Wrote my placeholder > define( ‘DYNAMIC_CACHE_TEST_TAG’ **‘dynamiccontent’** );// Changed this to a secret placeholder tag // in dynamic-cache-test.php and upladed it back in WP Super Cache/plugins folder. * I also replaced add_cacheaction( ‘wpsc_cachedata_safety’, ‘dynamic_output_buffer_test_safety’); with add_cacheaction( ‘wpsc_cachedata_safety’, ‘dynamic_cache_test_safety’ ); * All these steps are correct? * And is this worng ? * I have to use this Loading cart… where I want dynamic content to appear? * [0utf1t](https://wordpress.org/support/users/0utf1t/) * (@0utf1t) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245058) * Ok, if I paste your code in functions.php my site crashes. Where do you define(‘ DYNAMIC_OUTPUT_BUFFER_TAG’, ” ); // Change this to a secret placeholder tag ? If I define in dynamic-cache-test.php and put back in wp super cache plugins folder, my site still crashes. 🙁 * Thread Starter [stebcom](https://wordpress.org/support/users/stebcom/) * (@stebcom) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245060) * I worked on this a lot of time ago, so I don’t remember that much. I think I gave up on Dynamic Cache Tag (the first option) because it didn’t work the way I needed, calling my functions ecc. Speaking about the output buffer: the code is still quite simple. You can define your constant where you prefer, like this: * `define( 'DYNAMIC_OUTPUT_BUFFER_TAG', 'Your placeholder' );` * The dynamic cache is not the only option to keep part of your pages dynamic, anyway: if you have issues with that, you should try loading your content via ajax. * [0utf1t](https://wordpress.org/support/users/0utf1t/) * (@0utf1t) * [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245061) * So you defined you constnat define( ‘DYNAMIC_OUTPUT_BUFFER_TAG’, ‘Your placeholder’); in dynamic-cache-test.php and upladed it back in WP Super Cache/plugins folder. Is that correct? In your case it was minicart, right? * And the you inserted code in to functions.php and templte page which you mentioned before? * and thats it? * oh I’m really lost into this, and it drives me nuts that I can’t get it work. * Any chance you know a link for that ajax tutorial? * I just want my date to be dynamic. * Thanks anyway for your help! Viewing 8 replies - 1 through 8 (of 8 total) The topic ‘Fatal error trying using dynamic content’ is closed to new replies. * ![](https://ps.w.org/wp-super-cache/assets/icon-256x256.png?rev=3506220) * [WP Super Cache](https://wordpress.org/plugins/wp-super-cache/) * [Frequently Asked Questions](https://wordpress.org/plugins/wp-super-cache/#faq) * [Support Threads](https://wordpress.org/support/plugin/wp-super-cache/) * [Active Topics](https://wordpress.org/support/plugin/wp-super-cache/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/wp-super-cache/unresolved/) * [Reviews](https://wordpress.org/support/plugin/wp-super-cache/reviews/) ## Tags * [buffer](https://wordpress.org/support/topic-tag/buffer/) * [dynamic cache](https://wordpress.org/support/topic-tag/dynamic-cache/) * [php](https://wordpress.org/support/topic-tag/php/) * 8 replies * 2 participants * Last reply from: [0utf1t](https://wordpress.org/support/users/0utf1t/) * Last activity: [11 years, 3 months ago](https://wordpress.org/support/topic/fatal-error-trying-using-dynamic-content/#post-5245061) * Status: not resolved