AJAX send data to PHP file - php

Question

send $username php with data: new FormData(this), to add.php like data: new FormData(this),$username how can i do it with ajax code
<script type="text/javascript">
$(document).ready(function (e) {
$("#uploadFormuserimg").on('submit',(function(e) {
e.preventDefault();
$.ajax({
url: "add.php",
type: "POST",
data: new FormData(this),
contentType: false,
cache: false,
processData:false,
success: function(data)
{
$("#user_img_a").html(data);
},
error: function()
{ alert("error");
}
});
}));
});
</script>

Answer 1

var myData = new FormData(this);
myData.append('username','<?php echo $username; ?>');
and get on "add.php" like this
$username = $_POST['username'];
This worked on my side.

Answer 2

Based on comments to the question, specifically:
I just want to add some data
Are you just asking how to add more fields to the object that was created already in the data value? Something like this:
var myData = new FormData(this);
myData.append("anotherField", "anotherValue");
// etc.
Then just use that variable as your AJAX data:
$.ajax({
url: "add.php",
type: "POST",
data: myData,
contentType: false,
cache: false,
processData:false,
success: function(data)
{
$("#user_img_a").html(data);
},
error: function()
{ alert("error");
}
});
You can store anything you like in a variable and use that variable at a later time. With a FormData object you would generally use .append() to add more key/value pairs to it.