I have update my Joomla from V3.4 to V3.5 and below error is showing.

I tried to place die('here'); in administrator/components/com_ajax/ajax.php and there is no output.

• In the Joomla backend, go to Extensions >> Manage >> Manage, then see if Ajax Interface is in the list of installed extensions – Lodder May 3 '16 at 8:24
• only plg_ajax_zentools2  found. – urfusion May 3 '16 at 8:25
• I just check in default joomla 3.5 there is no ajax in Extensions >> Manage >> Manage – urfusion May 3 '16 at 8:26
• Ok now try going to Extensions >> Manage >> Discover. If you see it there, install it – Lodder May 3 '16 at 8:31