Fatal error: Uncaught Error: Call to undefined function is_plugin_active() in /home/sakurai0717/advance20.com/public_html/wp-content/plugins/rich-table-of-content/functions.php:519 Stack trace: #0 /home/sakurai0717/advance20.com/public_html/wp-content/plugins/rich-table-of-content/functions.php(698): rtoc_get_index('<h2 id="rtoc-1"...') #1 /home/sakurai0717/advance20.com/public_html/wp-includes/class-wp-hook.php(303): rtoc_switch_mokuji('<h2 id="rtoc-1"...') #2 /home/sakurai0717/advance20.com/public_html/wp-includes/plugin.php(189): WP_Hook->apply_filters('<h2>\xE9\x9D\xB4</h2>\n<h...', Array) #3 /home/sakurai0717/advance20.com/public_html/wp-includes/post-template.php(253): apply_filters('the_content', '<h2>\xE9\x9D\xB4</h2>\r\n<...') #4 /home/sakurai0717/advance20.com/public_html/wp-content/themes/tree_tcd081/page.php(73): the_content() #5 /home/sakurai0717/advance20.com/public_html/wp-includes/template-loader.php(106): include('/home/sakurai07...') #6 /home/sakurai0717/advance20.com/public_html/wp-blog-header.php(19): in /home/sakurai0717/advance20.com/public_html/wp-content/plugins/rich-table-of-content/functions.php on line 519