Fatal error saving table – DOMDocument ValueError on PHP 8

  • smartfinds

    (@smartfinds)


    2 months ago

    Hi WP Table Builder Team,

    We’re encountering a fatal error when saving a table on our WordPress site (smartfindsmarketing.com). The issue occurs via admin-ajax.php when performing a “Save Table” action.

    Below is the relevant error excerpt from our debug.log file:

    PHP Fatal error:  Uncaught ValueError: DOMDocument::loadHTML(): Argument #1 ($source) must not be empty
in /wp-content/plugins/wp-table-builder/vendor/rhukster/dom-sanitizer/src/DOMSanitizer.php:326
Stack trace:
#0 /wp-content/plugins/wp-table-builder/vendor/rhukster/dom-sanitizer/src/DOMSanitizer.php(326): DOMDocument->loadHTML('')
#1 /wp-content/plugins/wp-table-builder/inc/Shortcode_Element.php(147): DOMSanitizer->sanitize('')
#2 /wp-content/plugins/wp-table-builder/inc/TableRenderer.php(234): Shortcode_Element->render()
#3 /wp-content/plugins/wp-table-builder/inc/Admin_Menu.php(429): TableRenderer->render_cell()
#4 /wp-includes/class-wp-hook.php(308): Admin_Menu->save_table()
#5 /wp-admin/admin-ajax.php(203): do_action('wp_ajax_save_table')

    What we’ve already checked:

    • Running PHP 8.0.
    • Confirmed no database errors.
    • The error triggers when a table includes a shortcode or possibly an empty cell.
    • Other unrelated plugin warnings (“Add Search to Menu”) are present but not the root cause.

    Hypothesis:
    It appears the plugin’s DOM sanitizer attempts to call DOMDocument::loadHTML() on an empty string, which PHP 8+ now treats as a ValueError. This may need a guard to skip empty input before sanitization.

    Questions:

    1. Can you confirm if this is a known issue with WP Table Builder on PHP 8.x?
    2. Is there a patch or temporary fix (e.g., conditional check) to prevent this error until an update is released?
    3. Would you like me to provide a sample table export or exact steps to reproduce it?

    Thank you for your time and for maintaining a great plugin!

Viewing 2 replies - 1 through 2 (of 2 total)
  • Plugin Contributor Saad

    (@protibimbok)

    2 months ago

    Thank you for your detailed report.
    1. No, it is not a known issue.
    2. You can replace the part in /wp-content/plugins/wp-table-builder/inc/Shortcode_Element.php with

    $shortcode = trim($props['shortcode'] ?? '');
    if (empty($shortcode)) {
    $code = '';
    } else {
    $sanitizer = new DOMSanitizer(DOMSanitizer::HTML);
    $code = $sanitizer->sanitize($shortcode, [
    'remove-html-tags' => false,
    ]);
    }
    3. Checking the instruction 2 would be more helpful.

    Thank you for sticking with us.

    Thread Starter smartfinds

    (@smartfinds)

    2 months ago

    Hi Saad,

    Thanks again for your earlier help with the PHP 8.0 ValueError issue. We followed your instructions to add the guard around the sanitizer, but wanted to note that the file path you provided (/inc/Shortcode_Element.php) does not exist in the current plugin version.

    In our installation, the correct file was located at:
    /inc/admin/element-classes/elements/shortcode-element.php

    We implemented the guard there, and it did stop the original DOMDocument::loadHTML() fatal error on PHP 8.0. However, after applying the change, we were no longer able to access WP Table Builder in WP Admin — it displayed “Sorry, you are not allowed to access this page.”

    We’ve since reverted the file to its original version, and the admin access issue disappeared immediately.

    So while the proposed guard fixes the fatal error itself, it appears to introduce a secondary issue in the current version of the plugin.

    Would you be able to review this behavior and confirm the correct placement or logic for the guard? We’d be happy to test a corrected version or updated build if you release one.

    Thanks again for your assistance,

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

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