Title: Unknown Modifier
Last modified: March 31, 2022

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# Unknown Modifier

 *  Resolved [mperry8304](https://wordpress.org/support/users/mperry8304/)
 * (@mperry8304)
 * [4 years ago](https://wordpress.org/support/topic/unknown-modifier-3/)
 * My client is getting a large error log at the root of her site. The error is:
   
   PHP Warning: preg_match(): Unknown modifier ‘a’ in wp-content/plugins/all-in-
   one-seo-pack/app/Common/Schema/Breadcrumb.php on line 107
 * The error has been occurring for months and started sometime after updating to
   All in One SEO 4.1.0.2. Updating to other versions of the software has not helped.
 * If you search for the error in Google, you see many other people are having this
   issue too.

Viewing 2 replies - 1 through 2 (of 2 total)

 *  Plugin Author [arnaudbroes](https://wordpress.org/support/users/arnaudbroes/)
 * (@arnaudbroes)
 * [4 years ago](https://wordpress.org/support/topic/unknown-modifier-3/#post-15521462)
 * Hey [@mperry8304](https://wordpress.org/support/users/mperry8304/),
 * Have you tried updating to the latest version already? This issue should have
   been fixed a while ago in our 4.1.6.1 release.
 * After updating, definitely make sure that you clear your site/server cache since
   the files and error might be cached.
 *  Thread Starter [mperry8304](https://wordpress.org/support/users/mperry8304/)
 * (@mperry8304)
 * [4 years ago](https://wordpress.org/support/topic/unknown-modifier-3/#post-15529882)
 * Thanks for your help. We’d been using All in One SEO 4.1.5.3 and just updated
   to All in One SEO 4.1.9.4. I can confirm that the error log is no longer being
   generated.

Viewing 2 replies - 1 through 2 (of 2 total)

The topic ‘Unknown Modifier’ is closed to new replies.

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## Tags

 * [preg_match](https://wordpress.org/support/topic-tag/preg_match/)
 * [unknown modifier](https://wordpress.org/support/topic-tag/unknown-modifier/)

 * 2 replies
 * 2 participants
 * Last reply from: [mperry8304](https://wordpress.org/support/users/mperry8304/)
 * Last activity: [4 years ago](https://wordpress.org/support/topic/unknown-modifier-3/#post-15529882)
 * Status: resolved