在页面加载时第一次加载ajax

On my PHP page I use AJAX to fetch items for an auction, everything is working properly when something is chosen from the dropdown lists (as can be seen from picture 1 ). My problem is that when the page loads for the first time (see second picture ) than nothing happens while I just want the default values of the dropdown list to be loaded in Ajax just like the rest, how do I go around this issue? Note that in the first picture I first selected something else and then selected the default values again, the 2nd picture is the page when i open up my browser and do nothing else.On my PHP page I use AJAX to fetch items for an