500 error at wp-admin / allowed memory exhausted / cannot use output buffering

  • This all started with a PHP upgrade from 7.0.9 to 7.2.9
    1) It works fine on DEV with 7.29 with the same plugins.
    2) Upgrading to 7.29 on LIVE allowed the site to function normally on the front-end, but got 500 internal server error when hitting wp-admin on the back end. Using incognito mode allowed wp-admin render, but then trying to login gave 500 internal server error
    3) PHP error log showed these errors
    [06-Feb-2019 22:11:35 UTC] PHP Fatal error:? Allowed memory size of 2097152 bytes exhausted (tried to allocate 1069056 bytes) in I:\xxxxxx\wp-content\plugins\w3-total-cache\Cache_Wincache.php on line 42
    [06-Feb-2019 22:11:35 UTC] PHP Fatal error:? Allowed memory size of 2097152 bytes exhausted (tried to allocate 65536 bytes) in I:\xxxxxxx\wp-content\plugins\w3-total-cache\Util_Content.php on line 4
    [06-Feb-2019 22:11:35 UTC] PHP Fatal error:? Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0
    4) Confirmed that the max memory size was 512m on both DEV and LIVE servers. I tried increasing LIVE to 1024m and still got the same exact error.

    Note: The W3TC plugin was updated to Version 0.9.7.2, prior to an update to WordPress 5.0.3 (from 4.9.9) and PHP 7.0.9 to 7.2.9 along with all other plugin updates, and tested to work perfectly on the DEV server. Everything was also updated and tested on the LIVE server, except the PHP 7.2.9 upgrade. It was working fine then too. The only thing that changed in the final step, was 7.0.9 to 7.2.9. The the wp-admin 500 error. I’m completely stumped on this. The web.config files are the same, but other than that, I’m at the mercy of our hosting to know whether everything else is the same.

    Ideas on what to try? Thx!

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

    (@vmarko)

    Hello,

    Are you using wincache for Object cache? It appears that some Big object (some plugin?) is stored there.
    The simplest solution is not to use object cache or increase memory limit or find out which plugin cause that big object.

    Thread Starter mhair

    (@mhair)

    Marko,

    I disabled object cache completely and purged the cache. I still get the 500 error when hitting wp-admin url. Here are the php errors.

    Here are the PHP errors:
    [07-Feb-2019 18:30:33 UTC] PHP Warning: Parameter 2 to search_by_title_only() expected to be a reference, value given in xxxx\wp-includes\class-wp-hook.php on line 286
    [07-Feb-2019 18:30:42 UTC] PHP Warning: Parameter 2 to search_by_title_only() expected to be a reference, value given in xxxx\wp-includes\class-wp-hook.php on line 286
    [07-Feb-2019 18:30:46 UTC] PHP Warning: Parameter 2 to search_by_title_only() expected to be a reference, value given in xxxx\wp-includes\class-wp-hook.php on line 286
    [07-Feb-2019 18:30:49 UTC] PHP Fatal error: Allowed memory size of 2097152 bytes exhausted (tried to allocate 32768 bytes) in xxxx\wp-content\plugins\pdfembedder-premium\core\EDD_SL_Plugin_Updater.php on line 349
    [07-Feb-2019 18:30:49 UTC] PHP Fatal error: Allowed memory size of 2097152 bytes exhausted (tried to allocate 32768 bytes) in xxxx\wp-content\plugins\w3-total-cache\Util_Content.php on line 1
    [07-Feb-2019 18:30:49 UTC] PHP Fatal error: Unknown: Cannot use output buffering in output buffering display handlers in Unknown on line 0

    So regarding memory, it complains about both the PDF Embedder plug-in and the W3TC this time, but no mention of Wincache. Also, have no idea what the output buffering error means.

    Does this tell you anything more? Really at my wits end because this means I’ll be stuck on PHP 7.0.9. Very agonizing to debug to because I have to ask hosting to revert to 7.0.9 each time to even get access to wp-admin to change things. And again, my dev server that is configured exactly the same (supposedly) is not showing this issue.

    Thanks for any insights you can provide on how to fix/troubleshoot this.

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