PHP Fatal error: Allowed memory size (WordPress 6.8)

  • aneimo

    (@aneimo)


    1 week, 6 days ago

    I can’t use Query Monitor on local site. In admin i’m getting PHP Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 266240 bytes) in HIDDEN-FULL-PATH/web/wp-content/plugins/query-monitor/classes/Backtrace.php on line 137

    OS: Zorin OS 17.3 x86_64
    Web server: nginx/1.26.3 (Valet Linux v2.3.11)
    PHP: 8.3
    DB: mysql Ver 15.1 Distrib 10.6.21-MariaDB
    Browser: Latest Chrome on Linux

    How I tested:
    Clean site install (WordPress 6.8).
    Removed all themes (except Twenty Twenty-Five) and plugins.
    Active theme is Twenty Twenty-Five (v 1.2).
    In wp-config.php set define( 'QM_ENABLE_CAPS_PANEL', true );
    Install Query Monitor.
    Trying activate Query Monitor. Getting PHP Fatal error: Allowed memory size of 1073741824 bytes exhausted (tried to allocate 266240 bytes) in HIDDEN-FULL-PATH/web/wp-content/plugins/query-monitor/classes/Backtrace.php on line 137.
    Open front-end. Front-end is working without errors.
    Trying open back-end and getting PHP Fatal error.
    Renaming query-monitor folder to query-monitor-bcp and then back-end and front-end working again.
    In wp-config.php set define( 'QM_ENABLE_CAPS_PANEL', false );
    Renaming query-monitor-bcp folder to query-monitor and activating Query Monitor plugin. This time back-end and front-end working as expected. No errors.

    • This topic was modified 1 week, 6 days ago by aneimo. Reason: Made another error testing
Viewing 4 replies - 1 through 4 (of 4 total)
  • psimatrix

    (@psimatrix)

    6 days, 5 hours ago

    I’m getting a similar issue:

    [02-May-2025 19:06:38 UTC] PHP Notice: ob_end_flush(): Failed to send buffer of zlib output compression (0) in [redacted]/public_html/wp-includes/functions.php on line 5471

    [02-May-2025 19:07:17 UTC] PHP Fatal error: Allowed memory size of 2147483648 bytes exhausted (tried to allocate 20480 bytes) in [redacted]/public_html/wp-content/plugins/query-monitor/classes/Backtrace.php on line 137

    [02-May-2025 19:07:17 UTC] PHP Fatal error: Allowed memory size of 2147483648 bytes exhausted (tried to allocate 65536 bytes) in [redacted]/public_html/wp-includes/class-wp-fatal-error-handler.php on line 43

    Thread Starter aneimo

    (@aneimo)

    6 days, 5 hours ago

    My problem was solved when I set define( 'QM_ENABLE_CAPS_PANEL', false ) in wp-config.php Acording Query Monitor documentation: “The user capabilities panel is not enabled by default because it can cause performance issues on sites that perform a large number of user capability checks.”. But… Before WordPress 6.8, there were no problems on the same site even when define( 'QM_ENABLE_CAPS_PANEL', true ) was enabled. The error has only appeared since WordPress 6.8

    Remco

    (@rembem)

    3 days, 9 hours ago

    Chiming in here. My memory errors look like below. It takes my server down each time I enable QM.

    I also have define( 'QM_ENABLE_CAPS_PANEL', true ) in wp-config.php, but for a long time. This issue started with WP6.8.

    [05-May-2025 14:57:47 UTC] PHP Fatal error: Allowed memory size of 3221225472 bytes exhausted (tried to allocate 528384 bytes) in [redacted]/public_html/wp-content/plugins/query-monitor/classes/Backtrace.php on line 318

    [05-May-2025 14:57:47 UTC] PHP Fatal error: Allowed memory size of 3221225472 bytes exhausted (tried to allocate 20480 bytes) in [redacted]/public_html/wp-includes/capabilities.php on line 1306

    [05-May-2025 15:11:58 UTC] PHP Fatal error: Allowed memory size of 3221225472 bytes exhausted (tried to allocate 528384 bytes) in [redacted]/public_html/wp-content/plugins/query-monitor/classes/Backtrace.php on line 318

    [05-May-2025 15:11:58 UTC] PHP Fatal error: Allowed memory size of 3221225472 bytes exhausted (tried to allocate 20480 bytes) in [redacted]/public_html/wp-includes/capabilities.php on line 1289
    • This reply was modified 3 days, 9 hours ago by Remco.
    Plugin Author John Blackbourn

    (@johnbillion)

    WordPress Core Developer

    10 hours, 54 minutes ago

    The short answer is that this is the reason the user capabilities panel is not enabled by default. Unfortunately it’s too easy for a site to perform a gigantic number of user capability checks, and Query Monitor can exhaust the available memory when it logs them.

    I’ll have a look to see what changed in WordPress 6.8 which might cause the further increase in memory usage, but I have some other higher priority tasks that I will probably need to address before that.

    Cheers!

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