Wordpress critical error - Uncaught Error: Class 'DOMDocument' not found in /site/wp-content/plugins/fb-instant-articles/vendor/facebook/facebook-instant-articles-sdk-php/src/Facebook/InstantArticles/Transformer/Transformer.php:247

[diegosantamarta]

Steps required to reproduce the problem

Editing some posts the Wordpress break. We lose all changes, preview, save buttons blocked and sometimes Wordpress critical error and tell us to review the email.

Expected Result

Be able to edit posts without any issue

Actual Result

When we check the email it says this:

Se ha producido un error del tipo E_ERROR en la línea 247 del archivo /site/wp-content/plugins/fb-instant-articles/vendor/facebook/facebook-instant-articles-sdk-php/src/Facebook/InstantArticles/Transformer/Transformer.php. Mensaje de error: Uncaught Error: Class 'DOMDocument' not found in /site/wp-content/plugins/fb-instant-articles/vendor/facebook/facebook-instant-articles-sdk-php/src/Facebook/InstantArticles/Transformer/Transformer.php:247
Stack trace:
#0 /site/wp-content/plugins/fb-instant-articles/class-instant-articles-post.php(644): Facebook\InstantArticles\Transformer\Transformer->transformString(Object(Facebook\InstantArticles\Elements\Header), 'Jos\xC3\xA9 Bay\xC3\xB3...', 'UTF-8')
#1 /site/wp-content/plugins/fb-instant-articles/class-instant-articles-post.php(873): Instant_Articles_Post->to_instant_article()
#2 /site/wp-content/plugins/fb-instant-articles/class-instant-articles-post.php(950): Instant_Articles_Post->is_empty_after_transformation()
#3 /site/wp-content/plugins/fb-instant-articles/facebook-instant-articles.php(538): Instant_Articles_Post->should_submit_post()
#4 /site/wp-includes/class-wp-hook.p

Version Info

WordPress versión 5.3.2 Plugin actual: Instant Articles for WP (versión 4.2.0) PHP versión 7.3.14-1+ubuntu16.04.1+deb.sury.org+1