Compression via PHP documented and in URL but not used anymore

[zodiac1978]

It looks like these three constants are not used anymore:

define( ‘COMPRESS_CSS’, true );
define( ‘COMPRESS_SCRIPTS’, true );
define( ‘ENFORCE_GZIP’, true )

In #44815 the check for the "c" parameter (for compression) in load-scripts.php and load-styles.php was removed.

But it is still used in this file:
​https://github.com/WordPress/WordPress/blob/master/wp-includes/script-loader.php#L2199
and
​https://github.com/WordPress/WordPress/blob/master/wp-includes/script-loader.php#L2377

And documented at the beginning of the file:
​https://github.com/WordPress/WordPress/blob/master/wp-includes/script-loader.php#L8-L10

It looks like we can safely remove this or is there a reason to keep it?

Remove legacy compression constants (COMPRESS_SCRIPTS, COMPRESS_CSS, ENFORCE_GZIP) and related code.

Trac ticket: #63017

[zodiac1978]

Hi @sainathpoojary

thanks for the patch! It looks great.

I think we could modify some more of the inline docs:

* Several constants are used to manage the loading, concatenating and compression of scripts and CSS:

could maybe changed to something like:

* These constants are used to manage the loading and concatenating of scripts and CSS:

And

 * The globals $concatenate_scripts, $compress_scripts and $compress_css can be set by plugins
 * to temporarily override the above settings. Also a compression test is run once and the result is saved

could maybe changed to:

 * The global $concatenate_scripts can be set by plugins to temporarily override the above 
 * setting.

[zodiac1978]

#44815 was from milestone 4.9.9, but in the version dropdown 4.9.9 is missing, so I chose 5.0 which was the first major version with this change.

[sainathpoojary]

Hey @zodiac1978,

I’ve updated the documentation based on your suggestion. Whenever you have a moment, I’d appreciate it if you could take a look. Thank you!

[zodiac1978]

@sainathpoojary Thanks for the updated patch! Looks good to me.

In the latest devchat I asked for feedback - starting here:
​https://wordpress.slack.com/archives/C02RQBWTW/p1741794112933009

@joemcgill, @desrosj and @joedolson have raised some concerns about the usage in plugins. I've checked every search result in the official directory, and this is only used in system reports / debugging info. Sometimes it is set to false if not defined, and only one or two times a very old plugin tries to set it according to its own option.

But no plugin uses PHP compression if this constant is set to true.

COMPRESS_CSS (95 matches in 44 plugins)
​https://wpdirectory.net/search/01JPNFP946XW7V4MFBP1CRMCNW

COMPRESS_SCRIPTS (97 matches in 46 plugins)
​https://wpdirectory.net/search/01JPNFQRT2WGMS9C2HCAHC271K

ENFORCE_GZIP (53 matches in 29 plugins)
​https://wpdirectory.net/search/01JPNFRB89HF670GMJB8PWKJ95

As described in the description, core does not use this anymore intentionally since #44815, but there is a dev note missing about the deprecation of this constant.

A search for COMPRESS_CSS and ENFORCE_GZIP in core only shows two findings, one in debug data and one for the mentioned file:

​https://github.com/search?q=repo%3AWordPress%2FWordPress%20COMPRESS_CSS&type=code
​https://github.com/search?q=repo%3AWordPress%2FWordPress+ENFORCE_GZIP&type=code

Only COMPRESS_SCRIPTS shows more results, but only because the phrase catches "can_compress_scripts" too:
​https://github.com/search?q=repo%3AWordPress%2FWordPress+COMPRESS_SCRIPTS&type=code

With quotes, it shows the same results:
​https://github.com/search?q=repo%3AWordPress%2FWordPress+%27COMPRESS_SCRIPTS%27&type=code

As the component maintainer, maybe @azaozz can now decide on this research that this constant is unused and should be officially announced as deprecated. I would suggest adding a dev note to inform plugin authors about it, so they can remove it from those debug reports.

Maybe @SergeyBiryukov can also shed some light to why this wasn't deprecated at the time of the remove of the underlying code.

Additionally, we should open a new trac ticket for removing those constants from our own Health Check debug report.

This looks good. I hope I'll have time this weekend to go over it in more details. One thing to note is that the global $compress_scripts and $compress_css as set in script_concat_settings() would still need to exist for full backwards compatibility.

Would it also be possible to remove checking these constants from class-wp-debug-data.php?

[azaozz]

The PR looks good but seems to need a bit more work. Use of these constants in plugins seem to be mostly in code that was copied from core at some point. Imho it is quite safe to assume that compression of scripts and stylesheets from PHP is undesirable, so setting the deprecated constants to false in core should be fully backwards compatible.

Seems it would be best to add this together with the closely related #58302 (that also needs some more work). Even thinking these two tickets can be merged together.

[westonruter]

Punting to Future Release to accompany #58302