WP Admin memory limit not increasing to base limit by default

[eclare]

We have 2 constants that can be set in wp-config.php (and by using filters, afaik), for example:

define( 'WP_MEMORY_LIMIT', '512M' ); // increases WP base (front-end) limit
define( 'WP_MAX_MEMORY_LIMIT', '512M'); // increases WP admin (back-end) limit

The former isn't really known, which you can Google to find out. People usually only use the first constant.
If the 2nd constant (WP_MAX_MEMORY_LIMIT) is not set, it defaults to 256M. WP_MEMORY_LIMIT can be higher than that though, so we could safely increase WP_MAX_MEMORY_LIMIT to match WP_MEMORY_LIMIT if WP_MEMORY_LIMIT is higher and WP_MAX_MEMORY_LIMIT is not set manually to a lower (than WP_MEMORY_LIMIT) value.

What I mean in coding terms:

if(!isset(WP_MAX_MEMORY_LIMIT) && isset(WP_MEMORY_LIMIT)){
    if(WP_MEMORY_LIMIT>DEFAULT_WP_MAX_MEMORY_LIMIT){
    //NOTE to the line above: this requires parsing the actual value in these constants as the strings can be like: 512M, 1G etc.; the DEFAULT_WP_MAX_MEMORY_LIMIT is a thing I came up with, currently the default admin memory limit is 256M
        define( 'WP_MAX_MEMORY_LIMIT', WP_MEMORY_LIMIT);
    }
}

All these values can be checked with the Bulletproof Security plugin, under BPS Security -> System Info.
Side note: imho WP_MAX_MEMORY_LIMIT should be renamed to something like WP_ADMIN_MEMORY_LIMIT, but that's another issue.

[dd32]

This seems like a sane enough change to me.

36426.diff​ sets WP_MAX_MEMORY_LIMIT to WP_MEMORY_LIMIT in the event that WP_MEMORY_LIMIT is > 256M.

[eclare]

Code looks good to me, but I'm no core dev. Thanks!

The code for setting the WP_MAX_MEMORY_LIMIT has been tweaked. If the defined WP_MEMORY_LIMIT in bytes is greater than 256M, WP_MAX_MEMORY_LIMIT will now be set to the value of WP_MEMORY_LIMIT instead of the current memory limit. This adjustment provides a more precise control of the memory limit.

[pbearne]

refreshed

[flixos90]

In 58937:

Administration: Avoid using WP_MAX_MEMORY_LIMIT default that is smaller than WP_MEMORY_LIMIT.

Props eclare, dd32, pbearne.
Fixes #36426.

Committed in https://core.trac.wordpress.org/changeset/58937