javascript - What is wrong with this post submission method?

The data cannot be inserted after submission. Is it because I wrote it in ajax?
tt.php

    
    
    




    
    提交

ajax.php

prepare("insert into ajax(txt)values(?)");
$stmt->execute(array($txt));
?>

Reply content:

The data cannot be inserted after submission. Is it because I wrote it in ajax?
tt.php

    
    
    




    
    提交

ajax.php

prepare("insert into ajax(txt)values(?)");
$stmt->execute(array($txt));
?>

1. Clicking the submit button will trigger the onsubmit event by default, but the onclick event you bound to it does not cancel the default event;

oBtn.onclick=function(e){
    var e=window.event||e;
    e.preventDefault&&e.preventDefault();
    e.returnValue&&e.returnValue=false;
}

2. Use the default onsubmit, ignore ajax, add name="aa" to txt1;

function ajax(url,data,funsucc){
            var oAjax=new XMLHttpRequest();
            oAjax.open('POST',url,true);                   
            oAjax.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
            oAjax.send("aa="+data);//在这里打个断点看看
            oAjax.onreadystatechange=function(){
              if(oAjax.readyState==4){
                if(oAjax.status==200){
                  funsucc(oAjax.responseText);
                }
             }
           }
        }

The ajax function is modified like this:

function ajax(url,data,funsucc){
            var oAjax=new XMLHttpRequest();
            oAjax.open('POST',url,true);                   
            oAjax.setRequestHeader("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");          
            oAjax.onreadystatechange=function(){
              if(oAjax.readyState==4){
                if(oAjax.status==200){
                  funsucc(oAjax.responseText);
                }
             }
           }
              oAjax.send("aa="+data);   
        }

Asynchronous call, otherwise the data cannot be sent