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Resolving Memory Limit Errors After Upgrading to PHP 8.2 or Higher

15 threads Sep 21, 2025 Core → Fixing wordpress

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Upgrading your server's PHP version is a great way to improve site performance and security. However, a common issue that can arise when moving from PHP 8.1 to 8.2 or 8.3 is the sudden appearance of 'Allowed memory size exhausted' fatal errors, even when your memory limit is set to a high value like 512MB. This guide will explain why this happens and walk you through the most effective solutions.

Why Does This Happen?

Newer versions of PHP (8.2, 8.3) often have stricter memory handling and may execute code paths differently than older versions. A plugin or theme that functioned within the memory limits on PHP 8.1 might attempt to allocate memory in a less efficient way under the new version, triggering the limit. The error messages often point to specific files in your plugins or themes, indicating where the problematic allocation is occurring.

How to Troubleshoot and Fix the Issue

1. Confirm Your Actual Memory Limit

The first step is to verify what memory limit WordPress is actually detecting. Sometimes, a configuration in a .user.ini or php.ini file can be overridden elsewhere.

  • Navigate to Tools > Site Health > Info in your WordPress admin dashboard.
  • Click on the Server tab.
  • Look for the PHP memory limit and PHP max input variables values. Ensure the memory limit matches what you expect (e.g., 512M).

2. Enable WordPress Debugging

To get more information about the error, enable debugging. Edit your wp-config.php file (located in your site's root directory) and make sure the following lines are present and set to these values:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );

This will create a debug.log file in your /wp-content/ directory that logs all errors, often providing more detail than the white screen of death.

3. Identify the Problematic Plugin or Theme

The error snippet usually names the file causing the problem. For example, an error in .../plugins/memberpress/... clearly points to the MemberPress plugin.

  • Deactivate all plugins and switch to a default WordPress theme like Twenty Twenty-Four.
  • Reactivate your theme and test. If the error returns, your theme is the culprit.
  • If the theme works fine, reactivate your plugins one by one, checking your site after each activation, until the error reappears.

4. Update Everything

Once you've identified a potentially problematic plugin or theme, check for updates. Developers frequently release patches for compatibility with newer PHP versions. An update is the easiest and most effective fix.

5. Increase the PHP Memory Limit

As a temporary workaround, you can try increasing the memory limit. This doesn't fix the root cause but can buy you time until a proper update is available. You can often do this through your hosting control panel (e.g., cPanel). Alternatively, you can add the following line to your wp-config.php file:

define( 'WP_MEMORY_LIMIT', '1024M' );

6. Contact the Developer

If a plugin or theme is causing the error and no update is available, report the issue to the developer. Provide them with the exact error message from your debug log. For instance, if the error is in the MemberPress plugin, you would contact the MemberPress support team.

Conclusion

Running into memory errors after a PHP upgrade can be frustrating, but it's usually a solvable problem. The process almost always involves identifying which piece of software isn't fully compatible with the new PHP version. By systematically disabling plugins, checking for updates, and using debugging tools, you can get your site back online and running efficiently on a modern, secure version of PHP.

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