如何从mysql表中逐行获取数据，使用jquery（AJAX）在php中编码的查询？

Question

I am a beginner in Ajax. I want to fetch data row from Subject Table consist of only one column Subject as varchar(100), defined in MySQL DB. Following is my php code.

Data.php

<?php

$con=mysqli_connect("","root","root","DBTemp") or die("</br> Error: " .mysqli_connect_error());

$sql="select * from Subject";
$result = mysqli_query($con,$sql);
while($row = mysqli_fetch_assoc($result))
 {
    echo $row["SUBJECT"];
    //I Want This Value to Be received in my Jquery Page
    //So that i can take certain action based on each Subject.
    //For example creating a select box child elements,options.
 }
?>

Jquery.js

$(document).ready(function()
 {
    var response='';
    $("body").ready(function()
     {
       $.ajax(
          {
            url: '/Data.php',
            type: 'GET'
            success: function(text)
                {
                     response=text;
                }
          });
     });
    $("body").append("<select> /*Get values here as options*/ </select>");
 });

But The Desired action is getting values row by row like:- 1st row value comes-> take certain action in jquery; 2nd row value comes-> take sertain action..; . . so on.

Answer 1

Data.php

<?php

$con=@mysqli_connect("","root","root","DBTemp");

# Instead of that use header 500 to let javascript side know there is a real error.

if (mysqli_connect_errno())
{
    echo "Could not connect to database : ". mysqli_connect_error();
    header($_SERVER['SERVER_PROTOCOL'] . ' 500 Internal Server Error', true, 500);
    exit();
}


$sql="select * from Subject";

$result = mysqli_query($con,$sql);

if (mysqli_error($con))
{
    echo "Query failed : ".mysqli_error($con);
    header($_SERVER['SERVER_PROTOCOL'] . ' 500 Internal Server Error', true, 500);
    exit();
}

$options = array();

# populate options arrey with using table's id field as key 
# and subject field as value.

while($row = mysqli_fetch_assoc($result))
{
    $options[$row['id']] = $row['subject'];

}

# return json encoded array to parse from javascript.
echo json_encode($options);

Data.php will output :

{"1":"Subject ID 1","2":"Subject ID 3"}

Jquery.js

$(document).ready(function()
{

    $("body").ready(function()
    {
        $.ajax(
                {
                    url: '/Data.php',
                    type: 'GET',
                    dataType: 'json',  // Let jQuery know returned data is json.
                    success: function(result)
                    {
                        $.each(result, function(id, subject) {
                            # Loop through results and add an option to select box.
                            $("#ajaxpopulate").append( new Option(subject,id) )
                        });

                    }
                });
    });

});

Page.html , inside the body. This select box will populated from ajax request.

 <select id="ajaxpopulate"></select>