PHP getting no response body - php

Question

Username and password values are being passed into my login php file and returning as a jsonResponse string. However the jsonResponse string that is being returning is empty?
<?php
# this file will return true or false depending if passed in username and password matcha user on the system.
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(-1);
$dbhost = "localhost";
$dbname = "example";
$dbuser = "example";
$dbpass = "example";
$conn = new PDO("mysql:host=$dbhost;dbname=$dbname",$dbuser,$dbpass);
$data = array( $_POST["username"],$_POST["password"] );
$stmt = $conn->prepare("Select * FROM example where username=?, password=?");
if(mysql_num_rows($stmt)>0)
{
$row = mysql_fetch_array($stmt);
if($_POST["password"] == $row["password"])
{
echo "loggedIn";
}
else
{
echo "passwordNotValid"; alert
}
}
else
{
echo "usernameNotValid";
}
if(!$stmt)
{
print_r($dbh->errorInfo());
}
}
?>

Answer 1

You have a lot of issues...
Remove the alert from that line
echo "passwordNotValid"; alert
Close the quotes like shown
echo "usernameNotValid";
Remove a } brace from the last line..
Apart from these issues... The (mysql_*) extension is deprecated as of PHP 5.5.0, and will be removed in the future. Instead,the MySQLi or PDO_MySQL extension should be used. Switching to PreparedStatements is even more better to ward off SQL Injection attacks !

Answer 2

you are mixing mysql_* with PDO. Here is a complete example of PDO. you should use PDO like this.
$dbhost = "localhost";
$dbname = "example";
$dbuser = "example";
$dbpass = "example";
$conn = new PDO("mysql:host=$dbhost;dbname=$dbname",$dbuser,$dbpass);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$stmt = $conn->prepare("Select * FROM example where username=?, password=?");
use your username and password varaibles in bind params
$stmt ->bindParam(':username', $username, PDO::PARAM_STR);
$stmt ->bindParam(':password', $password, PDO::PARAM_STR);
$stmt ->execute();
$result = $stmt ->fetch(PDO::FETCH_ASSOC);
and use $result in your page

Answer 3

Syntax error in line
echo "usernameNotValid;
your code is most likely never executed.