Issue in W3 Total Cache file and solution

Hello W3 team,

We are the developers of the Sirv WordPress plugin, https://wordpress.org/plugins/sirv/ which is used by many W3 Total Cache users.

We found a bug with the wp_resource_hints hook in this W3 Total Cache file:

/wp-content/plugins/w3-total-cache/UserExperience_Emoji_Extension.php

The issue is with the function that disables emojis. Here is the code from the file:

public function wp_resource_hints( $urls, $relation_type ) {
if ( !is_array( $urls ) || $relation_type != 'dns-prefetch' ) {
return $urls;
}

// remove s.w.org dns-prefetch used by emojis
return array_filter( $urls,
function( $v ) {
return ( substr( $v, 0, 16) != 'https://s.w.org/' );
}
);
}
}

The problem is that it does not work correctly with incoming parameters, as it can be an array of URLs or an array of resource attributes.

The WordPress documentation recommends to use an array:

wp_resource_hints

Can you please update the file to use an array?

We saw a similar issue in the Yoast SEO plugin and they fixed it like this:

public function resource_hints_plain_cleanup( $hints ) {
foreach ( $hints as $key => $hint ) {
if ( \is_array( $hint ) && isset( $hint['href'] ) ) {
if ( \strpos( $hint['href'], '//s.w.org' ) !== false ) {
unset( $hints[ $key ] );
}
}
elseif ( \strpos( $hint, '//s.w.org' ) !== false ) {
unset( $hints[ $key ] );
}
}
return $hints;
}

Without solving this issue, the following error occurs:

Fatal error: Uncaught TypeError: substr(): Argument #1 ($string)
must be of type string, array given in
/home/mysitecom/website/web/wp-content/plugins/w3-total-cache/UserExperience_Emoji_Extension.php:45
Stack trace: #0
/home/mysitecom/website/web/wp-content/plugins/w3-total-cache/UserExperience_Emoji_Extension.php(45):
substr(Array, 0, 16) #1 [internal function]:
W3TC\UserExperience_Emoji_Extension->W3TC\{closure}(Array)
#2 /home/mysitecom/website/web/wp-content/plugins/w3-total-cache/UserExperience_Emoji_Extension.php(43):
array_filter(Array, Object(Closure))
#3 /home/mysitecom/website/web/wp-includes/class-wp-hook.php(324):
W3TC\UserExperience_Emoji_Extension->wp_resource_hints(Array, 'dns-prefetch')
#4 /home/mysitecom/website/web/wp-includes/plugin.php(205):
WP_Hook->apply_filters(Array, Array)
#5 /home/mysitecom/website/web/wp-includes/general-template.php(3521):
apply_filters('wp_resource_hin...', Array, 'dns-prefetch')
#6 /home/mysitecom/website/web/wp-includes/class-wp-hook.php(324):
wp_resource_hints('')
#7 /home/mysitecom/website/web/wp-includes/class-wp-hook.php(348):
WP_Hook->apply_filters('', Array)
#8 /home/mysitecom/website/web/wp-includes/plugin.php(517):
WP_Hook->do_action(Array)
#9 /home/mysitecom/website/web/wp-admin/admin-header.php(132):
do_action('admin_print_sty...')
#10 /home/mysitecom/website/web/wp-admin/plugins.php(637):
require_once('/home/heskinsco...')
#11 {main} thrown in
/home/mysitecom/website/web/wp-content/plugins/w3-total-cache/UserExperience_Emoji_Extension.php on line 45

Looking forward to hearing from you.

Thank you,

The Sirv team
sirv.com