PHP 7.2 Warning: count(): Parameter must be an array or an object that implements Countable in /wp-includes/theme.php on line 356

[burlingtonbytes]

After upgrading to PHP 7.2 from 7.0 we observed PHP warnings on every pageload. It looks like get_theme_roots() runs count() on global $wp_theme_directories without checking the value first.

Proposed solution: check if empty($wp_theme_directories) before performing count().

patched version of get_theme_roots (wp-includes/theme.php line 356 in WP 4.9.4)

function get_theme_roots() {
	global $wp_theme_directories;

	if ( empty($wp_theme_directories) || count($wp_theme_directories) <= 1 )
		return '/themes';

	$theme_roots = get_site_transient( 'theme_roots' );
	if ( false === $theme_roots ) {
		search_theme_directories( true ); // Regenerate the transient.
		$theme_roots = get_site_transient( 'theme_roots' );
	}
	return $theme_roots;
}

We haven't observed this in a clean WordPress install, so we aren't sure why $wp_theme_directories would be empty, but this patch resolves the PHP warning while maintaining the existing, expected PHP <7.2 behavior.

[jrf]

Hi there and thanks for your report!

Please note that this is already being tracked in #42814.

Proposed solution: check if empty($wp_theme_directories) before performing count().

As a side-note, your proposed solution is definitely not the correct way to go about it as empty() will also return false on a non-empty string, a non-0 integer etc. and all of those would still cause the same warning to be thrown in PHP 7.2.

[burlingtonbytes]

Hi @jrf,

Thank you for your insight on the proposed solution.

If $wp_theme_directories should always be an array, then this conditional addresses the issue more comprehensively:
if ( empty($wp_theme_directories) || ( is_array($wp_theme_directories) && count($wp_theme_directories) <= 1 ) ) {

This way, we still return the default '/themes' if $wp_theme_directories is null, zero, or other invalid empty() value, OR is a valid array with 1 or fewer items. count() is only executed if is_array() passes.

I looked into #42814 before submitting this, but believe this to be a distinct issue because that ticket does not cover this specific use of count() in get_theme_roots(). The warning is effectively the same but in this case it is being generated in wp-includes/theme.php which is not referenced at all in #42814.

I may be missing something but I do not believe #42814 addresses this.

[jrf]

If $wp_theme_directories should always be an array, then this conditional addresses the issue more comprehensively:
if ( empty($wp_theme_directories) || ( is_array($wp_theme_directories) && count($wp_theme_directories) <= 1 ) ) {

Yes, however, now you're using a superfluous condition as the empty() is not needed is you first do an is_array(). Rewriting to the below would be simpler: (presuming $wp_theme_directories is always defined, otherwise an isset() would still be needed)

if ( ! is_array( $wp_theme_directories ) || count( $wp_theme_directories ) <= 1 ) ) {

I may be missing something but I do not believe #42814 addresses this.

AFAIK ticket #42814 is intended as the master ticket for these type of warnings, so I would suggest continuing the discussion there.

[ocean90]

A check for is_array() makes sense here. This would be consistent with wp_get_themes() for example.

#42814 is not a master ticket.

[teddytime]

This is a patch that resolves the warning

[desrosj]

#43583 will introduce an is_countable() polyfill for the PHP 7.3 function with the same name. I think it makes sense to start using that function here to fix this warning.

43374.patch​ utilizes the is_countable() function to avoid the PHP warning. Of course, this depends on the patch in #43583 being committed first.

[SergeyBiryukov]

In 43039:

Themes: Avoid a PHP 7.2 warning in get_theme_roots() when $wp_theme_directories is an uncountable value.

See [41174] for wp_get_themes() and get_raw_theme_root().

Props burlingtonbytes, teddytime, lbenicio, desrosj.
Fixes #43374. See #40109.

[SergeyBiryukov]

In 43040:

Themes: Avoid a PHP 7.2 warning in get_theme_roots() when $wp_theme_directories is an uncountable value.

See [41174] for wp_get_themes() and get_raw_theme_root().

Props burlingtonbytes, teddytime, lbenicio, desrosj.
Merges [43039] to the 4.9 branch.
Fixes #43374. See #40109.