How do we pass data in ajax?

Question

I am new to Ajax and I am confused as to how we pass data in Ajax. I have an index.php file which displays some data, it has a link to delete the record, now the problem is, I am not able to figure out how to transfer the id value from index.php of the selected record to ajax file. Also, how should I go about once I have fetched the value in delete.php page where lies the code to delete records. I have coded as below.

index.php

<div id="delMsg"></div>
<?php
$con=mysqli_connect("localhost","root","","ajaxtest");
$data=mysqli_query($con,"select * from member");
$col=mysqli_num_fields($data);
echo "<table>";
while($row=mysqli_fetch_array($data))
{
    echo "<tr>";
    for($i=0;$i<$col;$i++)
    {
        echo "<td>".$row[$i]."</td>";

    }
    echo "<td><a class='del' href='delete.php' data-ID=$row[0]>Delete</a></td>";
    echo"</tr>";
}
echo "</table>";
?>

ajax-file.js

$(document).ready(function(){
    $(".del").click(function(event){
    event.preventDefault();
    $.ajax({
        url:"delete.php",
        method:"get",
        data:{id:'ID'},
        dataType:"html",
        success:function(str){
            $('#delMsg').html(str);
            }

        })

    })  
})

delete.php

<?php
$id=$_GET['id'];

$con=mysqli_connect("localhost","root","","ajaxtest");
$data=mysqli_query($con,"delete from member where id='$id'");
if($data)
{
    echo "success"; 
}
else
{
    echo "error";   
}

?>

Answer 1

you should use what is called JSON ( Javascript Object Notation, I think). This will let you order your data better to do that you have to use, json_encode.

Now I am not exactly sure what you mean by this id value from index.php

But taking your index.php file, I would change it like this

//make sure the is no space here
<?php
//start output buffering
ob_start();
$html = ['<div id="delMsg"></div>'];
$con=mysqli_connect("localhost","root","","ajaxtest");
$data=mysqli_query($con,"select * from member");
$col=mysqli_num_fields($data);
$html[] = "<table>";
while($row=mysqli_fetch_array($data))
{
    $html[] = "<tr>";
    for($i=0;$i<$col;$i++)
    {
        $html[] = "<td>".$row[$i]."</td>";

    }
    $html[] = "<td><a class='del' href='delete.php' data-ID=$row[0]>Delete</a></td>";
    $html[] = "</tr>";
}
$html[] = "</table>";

$result = [
    'html' => implode("\n", $html),
    'debug' => ob_get_clean()
];

header("Content-type:application/json");
echo json_encode($result);

//?> ending tags are undesirable

Your JavaScript part will change too

$(document).ready(function(){
    $(".del").click(function(event){
    event.preventDefault();
    $.ajax({
        url:"delete.php",
        method:"get",
        data:{id:'ID'},
        dataType:"html",
        success:function(data){
            $('#delMsg').html(data.html);
            }

        })

    })  
})

You can see now that instead of just returning HTML, We will be returning it like this data in the Javascript and $result in php

{
  html : '<div id=" ...',
  debug : ""
}

I added ob_start and ob_get_clean this can be helpful because you cannot just echo content when outputting JSON, so this will catch any echo or print_r type content and put that into the debug item in the return.

Answer 2

Hopefully this conveys the idea of how an AJAX call works.

The first thing we want to do is setup our trigger, which in your case is a button with an onclick event.

<script
  src="http://code.jquery.com/jquery-3.3.1.min.js"
  integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8="
  crossorigin="anonymous"></script>

<!-- <button id="delete">Delete Something</button> -->
<button id="delete" onclick="onClickHandler(5)">Delete Something</button>

<p id="message">AJAX</p>

<script>
/* Notice I removed the document ready */
function onClickHandler(id)
{
    event.preventDefault();
    $.ajax(
    {
        url:"delete.php",
        method:"POST", /* In the real world you want to use a delete here */
        data: { /* plugin your data */
            id: id,
            name: "Bob",
            age: 25
        },
        dataType:"html",
        success: function(success)  {
            // Handle the success message here!

            if (success) {
                $('#message').text("Your message was received!");
            }
        },
        error: function(error) {
            // Handle your errors here
            $('#message').text("Something went wrong!");
        }
    });
};
</script>

Notice how my data is prepared in the data object. I leave it up to you to figure out how to grab data and set it in the right field. You could: $('#someId').value(); or pass it through a function. If this is a source of confusion I can clarify.

data: { /* plugin your data */
    id: 1,
    name: "Bob",
    age: 25
},

Next, we need to setup our script.

delete.php

<?php

    if ($_SERVER['REQUEST_METHOD'] == 'POST') {

        // Obviously validate the data.
        // But this is how you access it.
        // $_POST is a global array, so you can access it like so:
        $id = $_POST['id'];
        $name = $_POST['name'];
        $age = $_POST['age'];

        // Do your server side stuff...
        $sql = "DELETE FROM member
                WHERE id = '{$id}' AND name = '{$name}' AND age = '{$age}'";

        // Do your SQL (delete) here
        // $con = mysqli_connect("localhost","root","","ajaxtest");
        // Use prepared statements http://bobby-tables.com/php
        // $data = mysqli_query($con,"delete from member where id='$id'");

        // if ($data) { // Your condition

        // This is where you would check if the query passed
        // and send back the appropriate message.
        if ($id) {
            echo json_encode($id);
        }
        else {
            echo http_response_code(500);
        }
    }
    else {
        echo "You don't belong here!";
    }

Answer 3

Just replace

echo "<td><a class='del' href='delete.php' data-ID=$row[0]>Delete</a></td>";

To

echo "<td><a onclick="deleteRow($row[0])">Delete</a></td>";

Javascript

function deleteRow(recordID)
{
   event.preventDefault();
  $.ajax({
    type: "GET",
     url: "delete.php",
     data:{id: recordID}
    }).done(function( result ) {                    
      alert(result);
  });      
} 

In your PHP I recommend you to use PDO which is more easy and protected from SQL injection attacks. PHP:

    $db = new PDO('mysql:host=localhost;dbname=yourDB','root','');
$query = $db->prepare("Delete From yourTableName Where ID=:ID");
$id=$_GET['id'];
$query->bindParam('ID', $id);
$query->execute();

if ($query->rowCount()) {
    echo "success";
}
else
{
    echo "fails";
}