User Login Results in Fatal Error

  • Resolved Chocolalato

    (@lalato)


    6 years, 1 month ago

    Hi All,
    I am trying to figure out how to resolve an issue on my WordPress instance. Admin users have no trouble logging into the dashboard. However, when Editor (and below) users attempt to login, they get the following error:

    Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0

    The user appears to be logged in, but when they then try to go directly to the dashboard, the error is not there anymore, just a blank screen. Any ideas what might cause this?

    PHP: 7.0
    MySQL: 5.5.61
    WordPress: 5.0.3
    Theme: Twenty Seventeen
    Plugins: WooCommerce, AdvancedAds, Advanced Ads – Selling Ads, iThemes Security, WP-Markdown, WP-Piwik

    • This topic was modified 6 years, 1 month ago by Chocolalato.
Viewing 4 replies - 1 through 4 (of 4 total)

  • Try using Health Check plugin to isolate which plugin is causing the problem.
    https://www.ads-software.com/plugins/health-check/

    It allows you to disable plugins for the current user only (so it doesn’t affect your site visitors), and gives information about your site.

    Thread Starter Chocolalato

    (@lalato)

    Thanks for the tip, @joyously.

    When I used Health Check, it revealed the following…

    The required module, gd, is not installer, or has been disabled.
    The required module, mcrypt, is not installer, or has been disabled.

    I will work on getting these running to see if that resolves the issue.

    Thread Starter Chocolalato

    (@lalato)

    After installing those two PHP modules, the error message on login pinpointed the iThemes Security plugin as the cause of the login issue.

    I deactivated the plugin and users were able to login again without errors. Now I need to figure out why iThemes was causing the problem.

    Thanks again for pointing me to the Health Check plugin.

    Thread Starter Chocolalato

    (@lalato)

    The iThemes Security plugin was throwing a Fatal Error due to memory allocation. Upping the PHP memory limit to 64M seems to have resolved the issue for now. Users can login with the plugin Activated.

Viewing 4 replies - 1 through 4 (of 4 total)
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