Reduce memory usage in kses.php

[duck_]

Our allowed attributes rules in kses.php create a large number of empty arrays. These can all be replaced with true instead. This reduces memory usage by 62 kilobytes - not huge, but it all adds up.

This change is possible because the arrays are only used for attribute value checks, see wp_kses_attr(). Anything other than array just indicates that the attribute is allowed, see kses README and docs/attribute-value-checks for examples.

The block that filters style attributes with safecss_filter_attr() has to be moved out of the is_array() check to accommodate for this.

[nacin]

With the patch, array() will still work, right?

[duck_]

Replying to nacin:

With the patch, array() will still work, right?

Yes.

[duck_]

In [19976]:

Reduce memory usage in wp-includes/kses.php by switching unnecessary empty arrays to boolean. Fixes #20017.

safecss_filter_attr() block for style tags must be moved out of the is_array() only branch of wp_kses_attr() to accommodate for this.

[westi]

Great work!

[ocean90]

In 40637:

KSES: Support 'tag' => true as a shorthand for 'tag' => array() in wp_kses_attr().

Automatic_Upgrader_Skin::feedback() had always assumed that this is already the case, now it is.

See #20017.
Fixes #40680.