anwisystems/dist/js/laptopmuti.js

function callGallery(){
    $('.PO_gallery_box').each(function(i,el){
        $(el).click(function(e){
            const src = $(e.target).attr('src');
            $('.PO_gallery_display_img').attr('src',src)
        });
    });
}

function callMain(){
    callGallery();
}

callMain();