如何通过ajax用post类型间接调用php文件并获取json返回然后将其解析为表

I have 2 php file, one is "Db_function.php" and "index.php", "index.php" will make a function call in "Db_function.php". I want to make a call to "index.php" by ajax, here's my codeI have 2 php file, one is "Db_function.php" and