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>\xE5\x87\xBA\xE5\xBC\xB5\xE8\xB2\xB7\xE5\x8F...', Array) #3 /home/sakurai0717/advance20.com/public_html/wp-includes/post-template.php(253): apply_filters('the_content', '<h2>\xE5\x87\xBA\xE5\xBC\xB5\xE8\xB2\xB7\xE5\x8F...') #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/advan in /home/sakurai0717/advance20.com/public_html/wp-content/plugins/rich-table-of-content/functions.php on line 519