html表单字段在提交表单之前从sql数据库获取内容？

Question

I try to get content from database before submitting the form.I call javascript function in onload method.When I Directly write php code into textarea it works but when I append same php content to textarea through JS its not working, total php content only shown in textarea.Thanks in advance.

var parent=document.getElementById("textarea");
var child=document.createTextNode(' <?php '+
' include "conn.php"; '+
' $q1="SELECT `breakfast` FROM `foodmenu` WHERE `day`=\'Wednesday\'"; '+
' $result=$conn->query($q1); '+
' while($row=$result->fetch_assoc()) '+
' { '+
' echo $row["breakfast"]; '+
' } '+
' ?> ');
parent.appendChild(child);

Answer 1

call this method while load page, the field content get load from sql database. getmenu.php file have business logic to get query

$("select").on('change',function(){

    $.ajax({
        type: "POST",
        url: "getmenu.php",
        data: {
            day: $("#showday").val()  ,
            forwhat: $("#tab .active a").text()
        },
        success: function (Response) {
            $("#menu").val(Response.trim());
        } // you had an extra );
    });

});