"DataTables warning: table id=example - Ajax error."

I want to make a search table where in I can search the records I have from my database and it will show on a table in my website. I did use DataTable Using PHP, Mysql, Ajax, Json with server side script but I have an error that says "DataTables warning: table id=example - Ajax error."

What should I do to solve this problem? I am new to web programming and I need your help. Thank you so much.