Get Data From Server as Json Response

get_data.php

<?php 
require "conn.php";

if(isset($_POST["username"])) //always use isset function to skip unwanted request and error
{
	
	$query = mysqli_query($conn, "select * from android_data where username='$user_name'");
	
	if ($query) {
		while ($row = mysqli_fetch_array($query)) {
			$flag[] = $row;
		}
		echo(json_encode($flag));
	}

	$conn->close();
}

	//you can also use mysqli_fetch_assoc() for getting data as associative array skip serial
	//always stay in touch, stay with code. 
	//regards phpdark.com
?>