Inside a post title filter I check whether the current page is the blog page.
However, PHP complains that the function is_blog doesn’t exist:
NOTICE: PHP message: PHP Fatal error: Uncaught Error: Call to undefined function is_blog() in /srv/www/web/app/themes/some-theme/app/setup.php:339
php_1 | Stack trace:
php_1 | #0 /srv/www/web/wp/wp-includes/class-wp-hook.php(288): App\post_button_title('Some title', 6)
php_1 | #1 /srv/www/web/wp/wp-includes/plugin.php(206): WP_Hook->apply_filters('Some title', Array)
php_1 | #2 /srv/www/web/wp/wp-includes/post-template.php(171): apply_filters('the_title', 'Some title', 6)
php_1 | #3 /srv/www/web/wp/wp-includes/post-template.php(89): get_the_title(Object(WP_Post))
php_1 | #4 /srv/www/web/app/plugins/dublin-core-title/dublin-core-title.php(26): the_title_attribute(Array)
php_1 | #5 /srv/www/web/wp/wp-includes/class-wp-hook.php(288): add_dctitle('')
php_1 | #6 /srv/www/web/wp/wp-includes/class-wp-hook.php(312): WP_Hook->apply_filters(NULL, Array)
php_1 | #7 /srv/www/web/wp/wp-includes/plugin.php(478): WP_Hook->do_action(Array)
php_1 | #8 /srv/www/web/app/themes/some-theme/app/filters.php(52): do_action('wp_head')
php_1 | #9 /srv/www/web/app/themes/some-theme/vendor/illuminate/support/Collection.php(397): App\{closu in /srv/www/web/app/themes/some-theme/app/setup.php on line 339
In setup.php:
function post_button_title( $title, $post_id ) {
if(!\is_blog()) return $title; // skip
if(!$post_id) return $title; // skip
$button_title = get_field('button', $post_id);
if(!isset($button_title) or empty($button_title)) return $title; // skip
return $button_title;
}
add_filter( 'the_title', __NAMESPACE__ . '\\post_button_title', 10, 2 );
I already removed the wp/ folder for the WordPress installation and reinstalled using composer install.