Title: Error message: Unknown modifier Last modified: August 20, 2016 --- # Error message: Unknown modifier * Resolved [TT1](https://wordpress.org/support/users/tt1/) * (@tt1) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/) * I’ve just updated to version 1.3.4 and when I want to preview or save a draft of a post I get this error message: * > Warning: preg_match() [function.preg-match]: Unknown modifier ”’ in /var/sites/ > public_html/content/plugins/wordpress-seo/admin/class-metabox.php on line 1435 > Warning: Cannot modify header information – headers already sent by (output > started at /var/sites/public_html/content/plugins/wordpress-seo/admin/class- > metabox.php:1435) in /var/sites/public_html/wp-includes/pluggable.php on line > 876 * How do I fix this? * [http://wordpress.org/extend/plugins/wordpress-seo/](http://wordpress.org/extend/plugins/wordpress-seo/) Viewing 15 replies - 1 through 15 (of 24 total) 1 [2](https://wordpress.org/support/topic/error-message-unknown-modifier/page/2/?output_format=md) [→](https://wordpress.org/support/topic/error-message-unknown-modifier/page/2/?output_format=md) * [Tesur Rajan](https://wordpress.org/support/users/tesurrajan/) * (@tesurrajan) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283678) * Just updated…and see the same error. * [indigogirl](https://wordpress.org/support/users/indigogirl/) * (@indigogirl) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283691) * Me too 🙂 * [boah123](https://wordpress.org/support/users/boah123/) * (@boah123) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283695) * Me too. 🙁 * Warning: preg_match() [function.preg-match]: Unknown modifier ”’ in [..]\wp-content\ plugins\wordpress-seo\admin\class-metabox.php on line 1435 * [Martijnchel](https://wordpress.org/support/users/martijnchel/) * (@martijnchel) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283704) * Here also.. Everytime I publish a post. * [Weboxeur](https://wordpress.org/support/users/weboxeur/) * (@weboxeur) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283708) * **Edit:** The regex’s isn’t correctly formated. I tweeted Yoast about this, in meanwhile you can fix this by commenting the lines 1434 to 1437 in plugins/wordpress- seo/admin/class-metabox.php. * ``` /* foreach ( $matches[0] as $img ) { if ( preg_match( '|alt=("|\')(.*?)\1|', $img, $alt ) ) $imgs['alts'][] = $this->strtolower_utf8( $alt[2] ); } */ ``` * [Hazlo](https://wordpress.org/support/users/hazlo/) * (@hazlo) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283709) * Same here. I was just sending a post concerning the same issue meanwhile this one came out. Sorry for duplicating!! * [Guga Franke](https://wordpress.org/support/users/guga-franke/) * (@guga-franke) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283714) * Same problem here… How can i fix it? =\ * Plugin Contributor [Joost de Valk](https://wordpress.org/support/users/joostdevalk/) * (@joostdevalk) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283719) * Aargh, found: * changing: * `if ( preg_match( '|alt=("|\')(.*?)\1|', $img, $alt ) )` * on that line to: * `if ( preg_match( '/alt=("|\')(.*?)\1/', $img, $alt ) )` * fixes it. * Pushing an update. * Plugin Contributor [Joost de Valk](https://wordpress.org/support/users/joostdevalk/) * (@joostdevalk) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283721) * Version 1.3.4.1 should be there. * [isolde100](https://wordpress.org/support/users/isolde100/) * (@isolde100) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283723) * I got the same message today. Good to see others have the same problem. * [jasonsaulnier](https://wordpress.org/support/users/jasonsaulnier/) * (@jasonsaulnier) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283725) * I am having the same error as well. * [Franck Scipion](https://wordpress.org/support/users/ingresosalcuadrado/) * (@ingresosalcuadrado) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283726) * It does not fix the issue for me: * Warning: Cannot modify header information – headers already sent by (output started at ****/wp-content/plugins/wordpress-seo/admin/class-metabox.php:1435) in ****/ wp-includes/pluggable.php on line 876 * [negue.c](https://wordpress.org/support/users/neguec/) * (@neguec) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283730) * Upgrade 1.3.4.1 solved this “unknown modifier & cannot modify header info” for me. I just checked the source code of a post I published (using this WP SEO upgrade) and it’s all good. Thank you Joost! * [Webmistress89](https://wordpress.org/support/users/webmistress89/) * (@webmistress89) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283733) * The update fixed the error for me during Post update. * [isolde100](https://wordpress.org/support/users/isolde100/) * (@isolde100) * [13 years, 4 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/#post-3283737) * I downloaded this latest update and it fixed my problems. So disregard my previous message above in this thread. Viewing 15 replies - 1 through 15 (of 24 total) 1 [2](https://wordpress.org/support/topic/error-message-unknown-modifier/page/2/?output_format=md) [→](https://wordpress.org/support/topic/error-message-unknown-modifier/page/2/?output_format=md) The topic ‘Error message: Unknown modifier’ is closed to new replies. * ![](https://ps.w.org/wordpress-seo/assets/icon-256x256.gif?rev=3419908) * [Yoast SEO - Advanced SEO with real-time guidance and built-in AI](https://wordpress.org/plugins/wordpress-seo/) * [Frequently Asked Questions](https://wordpress.org/plugins/wordpress-seo/#faq) * [Support Threads](https://wordpress.org/support/plugin/wordpress-seo/) * [Active Topics](https://wordpress.org/support/plugin/wordpress-seo/active/) * [Unresolved Topics](https://wordpress.org/support/plugin/wordpress-seo/unresolved/) * [Reviews](https://wordpress.org/support/plugin/wordpress-seo/reviews/) * 24 replies * 17 participants * Last reply from: [Linda Lee](https://wordpress.org/support/users/ngb/) * Last activity: [12 years, 10 months ago](https://wordpress.org/support/topic/error-message-unknown-modifier/page/2/#post-3283808) * Status: resolved