[Résolu] Probleme avec function.php

function change_footer_version() {
    $current_theme_info = current_theme_info();
    return $current_theme_info->name . ' - Version ' . $current_theme_info->version;
}
add_filter( 'update_footer', 'change_footer_version', 999);

Fatal error: Uncaught Error: Call to undefined function is_blog_installed() in /home/makotokcod/www/wp-includes/load.php:540 Stack trace: #0 /home/makotokcod/www/wp-settings.php(140): wp_not_installed() #1 /home/makotokcod/www/wp-config.php(78): require_once('/home/makotokco...') #2 /home/makotokcod/www/wp-load.php(37): require_once('/home/makotokco...') #3 /home/makotokcod/www/wp-blog-header.php(13): require_once('/home/makotokco...') #4 /home/makotokcod/www/index.php(17): require('/home/makotokco...') #5 {main} thrown in /home/makotokcod/www/wp-includes/load.php on line 540

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_ob_end_flush_all' not found or invalid function name in /home/makotokcod/www/wp-includes/class-wp-hook.php on line 286