Title: 3.6 Missing functions Last modified: August 21, 2016 --- # 3.6 Missing functions * Resolved [sushi_nut](https://wordpress.org/support/users/sushi_nut/) * (@sushi_nut) * [12 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/) * Greetings all. * Tried to upgrade to 3.6 from 3.5.2 this morning and received errors about a function not existing or being invalid: * ``` Warning: call_user_func_array() expects parameter 1 to be a valid callback, function '_show_post_preview' not found or invalid function name in /home/USER/.../wp-includes/plugin.php on line 406 Warning: Cannot modify header information - headers already sent by (output started at /home/develop/macrumors-web-admin/wp-includes/plugin.php:406) in /home/USER/.../wp-includes/pluggable.php on line 875 ``` * Sure enough, it doesn’t exist in 3.6. Along with that, here are some others that were found after manually adding _show_post_preview: * ``` /** * Retrieve the format slug for a post * * @since 3.1.0 * * @param int|object $post A post * * @return mixed The format if successful. False if no format is set. WP_Error if errors. */ function get_post_format( $post = null ) { $post = get_post($post); if ( ! post_type_supports( $post->post_type, 'post-formats' ) ) return false; $_format = get_the_terms( $post->ID, 'post_format' ); if ( empty( $_format ) ) return false; $format = array_shift( $_format ); return ( str_replace('post-format-', '', $format->slug ) ); } function _show_post_preview() { if ( isset($_GET['preview_id']) && isset($_GET['preview_nonce']) ) { $id = (int) $_GET['preview_id']; if ( false == wp_verify_nonce( $_GET['preview_nonce'], 'post_preview_' . $id ) ) wp_die( __('You do not have permission to preview drafts.') ); add_filter('the_preview', '_set_preview'); } } /** * Determines if the specified post is a revision. * * @package WordPress * @subpackage Post_Revisions * @since 2.6.0 * * @param int|object $post Post ID or post object. * @return bool|int False if not a revision, ID of revision's parent otherwise. */ function wp_is_post_revision( $post ) { if ( !$post = wp_get_post_revision( $post ) ) return false; return (int) $post->post_parent; } /** * Gets a post revision. * * @package WordPress * @subpackage Post_Revisions * @since 2.6.0 * * @uses get_post() * * @param int|object $post Post ID or post object * @param string $output Optional. OBJECT, ARRAY_A, or ARRAY_N. * @param string $filter Optional sanitation filter. @see sanitize_post() * @return mixed Null if error or post object if success */ function wp_get_post_revision(&$post, $output = OBJECT, $filter = 'raw') { $null = null; if ( !$revision = get_post( $post, OBJECT, $filter ) ) return $revision; if ( 'revision' !== $revision->post_type ) return $null; if ( $output == OBJECT ) { return $revision; } elseif ( $output == ARRAY_A ) { $_revision = get_object_vars($revision); return $_revision; } elseif ( $output == ARRAY_N ) { $_revision = array_values(get_object_vars($revision)); return $_revision; } return $revision; } /** * Retrieve the autosaved data of the specified post. * * Returns a post object containing the information that was autosaved for the * specified post. * * @package WordPress * @subpackage Post_Revisions * @since 2.6.0 * * @param int $post_id The post ID. * @return object|bool The autosaved data or false on failure or when no autosave exists. */ function wp_get_post_autosave( $post_id ) { if ( !$post = get_post( $post_id ) ) return false; $q = array( 'name' => "{$post->ID}-autosave", 'post_parent' => $post->ID, 'post_type' => 'revision', 'post_status' => 'inherit' ); // Use WP_Query so that the result gets cached $autosave_query = new WP_Query; add_action( 'parse_query', '_wp_get_post_autosave_hack' ); $autosave = $autosave_query->query( $q ); remove_action( 'parse_query', '_wp_get_post_autosave_hack' ); if ( $autosave && is_array($autosave) && is_object($autosave[0]) ) return $autosave[0]; return false; } /** * Internally used to hack WP_Query into submission. * * @package WordPress * @subpackage Post_Revisions * @since 2.6.0 * * @param object $query WP_Query object */ function _wp_get_post_autosave_hack( $query ) { $query->is_single = false; } /** * Returns all revisions of specified post. * * @package WordPress * @subpackage Post_Revisions * @since 2.6.0 * * @uses get_children() * * @param int|object $post_id Post ID or post object * @return array empty if no revisions */ function wp_get_post_revisions( $post_id = 0, $args = null ) { if ( ! WP_POST_REVISIONS ) return array(); if ( ( !$post = get_post( $post_id ) ) || empty( $post->ID ) ) return array(); $defaults = array( 'order' => 'DESC', 'orderby' => 'date' ); $args = wp_parse_args( $args, $defaults ); $args = array_merge( $args, array( 'post_parent' => $post->ID, 'post_type' => 'revision', 'post_status' => 'inherit' ) ); if ( !$revisions = get_children( $args ) ) return array(); return $revisions; } ``` * Is anyone else having these errors? Some of these were found in revision.php but not all. Not a very graceful upgrade. Viewing 12 replies - 1 through 12 (of 12 total) * [esmi](https://wordpress.org/support/users/esmi/) * (@esmi) * [12 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998489) * Try: – switching to the default theme by renaming your current theme’s folder inside wp-content/themes and adding “-old” to the end of the folder name using [FTP](http://codex.wordpress.org/FTP_Clients) or whatever file management application your host provides. * – [resetting the plugins folder](http://codex.wordpress.org/FAQ_Troubleshooting#How_to_deactivate_all_plugins_when_not_able_to_access_the_administrative_menus.3F) by FTP or phpMyAdmin. * – re-uploading all files & folders – **except** the wp-content folder – from a **fresh** download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones. * – running the upgrade manually via wp-admin/upgrade.php * Thread Starter [sushi_nut](https://wordpress.org/support/users/sushi_nut/) * (@sushi_nut) * [12 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998507) * esmi, * Greatly appreciate the help; upgrade was finally successful. * [esmi](https://wordpress.org/support/users/esmi/) * (@esmi) * [12 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998514) * Excellent 🙂 * [sagbee](https://wordpress.org/support/users/sagbee/) * (@sagbee) * [12 years, 9 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998854) * so which one options worked for you? * [jmantalaba](https://wordpress.org/support/users/jmantalaba/) * (@jmantalaba) * [12 years, 9 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998869) * Hi, * I am also facing the same problem. However, want to know which options does it worked for you? Same as Sagbee’s question. * Up to this time, still could not figure how to solve the issues. * Thanks. * [NefertitiDesigns](https://wordpress.org/support/users/nefertitidesigns/) * (@nefertitidesigns) * [12 years, 9 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998876) * Similar problems for me after the update to 3.6, I had a page-template.php error so I: * – re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress, making sure to say override all existing files * and that fixed it. * [jmantalaba](https://wordpress.org/support/users/jmantalaba/) * (@jmantalaba) * [12 years, 9 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998877) * Hi, the problem has been fixed already by re-uploading WordPress files. This forum is so helpful. * [rk5075](https://wordpress.org/support/users/rk5075/) * (@rk5075) * [12 years, 9 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998943) * Thank you esmi, much obliged. * Identical issue solved by: * * database upgrade with wp-admin/upgrade.php * then uploading all folders manually, except wp-content * Very helpful thread. * [mobilewebexpert](https://wordpress.org/support/users/mobilewebexpert/) * (@mobilewebexpert) * [12 years, 8 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998965) * I had a very similar error message… “call_user_func_array() expects parameter 1 to be a valid callback, function ‘false’ not found or invalid function name in…” …showing at the top of my page. * I fixed it by changing this line in my functions.php file… `add_filter('show_admin_bar',' false');` …to… `add_filter( 'show_admin_bar', '__return_false' );` * [tomacpace](https://wordpress.org/support/users/tomacpace/) * (@tomacpace) * [12 years, 4 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998981) * I ran into this same problem and followed the recommendations by esmi. This was after I had already updated to the latest WP version, and the site was still working. I thought it may have been due to a plugin I was working on. But I’m just learning how to work with the entire WP plugin architecture. So my database was up-to-date. * However, the first point: * > – switching to the default theme by renaming your current theme’s folder inside > wp-content/themes and adding “-old” to the end of the folder name using FTP > or whatever file management application your host provides. * … doesn’t cause WP to automatically revert to the default theme. It didn’t for me, in any case. * After applying all of the suggested steps, the error went away but the site was totally blank. So, I removed the “-old” suffix on my theme folder, and voila! the site is fixed. * I am not a master WP engineer, and I appreciate the suggestions esmi. Awesome stuff. * [askwarok1](https://wordpress.org/support/users/askwarok1/) * (@askwarok1) * [11 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998996) * I really really need someones help. I have these two warnings: * Warning: call_user_func_array() expects parameter 1 to be a valid callback, function‘ _show_post_preview’ not found or invalid function name in /home/askwarok1/amandaskwarok. com/wp-includes/plugin.php on line 406 * Warning: Cannot modify header information – headers already sent by (output started at /home/askwarok1/amandaskwarok.com/wp-includes/plugin.php:406) in /home/askwarok1/ amandaskwarok.com/wp-includes/pluggable.php on line 874 * My hosting site automatically upgraded me to php5 and this is what happened. * I have already tired: * -everything listed by esmi’s advice. -I tried reverting back to the old php 5.2 -I updated and reloaded the new wordpress files (includes and admin) -I deleted and reuploaded wp-login. -I deactivated my plugins content-plugins -renamed theme to -old * I feel like I really tried but to no avail… I’m a freelance designer so you can imagine how stressful this is as this is my job… * If anyone could help me I would be so so greatfull! 🙂 * [esmi](https://wordpress.org/support/users/esmi/) * (@esmi) * [11 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998997) * If you require assistance then, as per the [Forum Welcome](http://codex.wordpress.org/Forum_Welcome#Where_To_Post), please post your own topic instead of tagging onto someone else’s topic. * I am now closing this 10 month old topic as it references very old version of WordPress. Viewing 12 replies - 1 through 12 (of 12 total) The topic ‘3.6 Missing functions’ is closed to new replies. * In: [Fixing WordPress](https://wordpress.org/support/forum/how-to-and-troubleshooting/) * 12 replies * 9 participants * Last reply from: [esmi](https://wordpress.org/support/users/esmi/) * Last activity: [11 years, 10 months ago](https://wordpress.org/support/topic/36-missing-functions/#post-3998997) * Status: resolved ## Topics ### Topics with no replies ### Non-support topics ### Resolved topics ### Unresolved topics ### All topics