MySQL select doesn't select - php

Question

I have been through quite some different codes on this site. To find what wrong with my code. Basically I just want to search in a table and test the result. I wrote something like this:
<?php
ob_start();
session_start();
$conn = new mysqli('localhost','username','password','mytable');
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$valuetotest = 'something';
$result = mysql_query("SELECT id FROM members WHERE UserName = $valuetotest");
if(mysql_num_rows($result) == 0)
{
echo "User not found";
}
$password = 'something2';
$userData = mysql_fetch_array($result, MYSQL_ASSOC);
if($password != $userData['Password'])
{
echo "Password not found";
}else{ // Redirect to home page after successful login.
header('Location: welcome.php');
}
?>
And I get always the message :
"User not found." and "password not found."
when I know the username and password are in the table...
No I'm quite knew with PHP/MySQL so there might be something quite big right in front of my face and I can't see it!!!!
Can somebody help please. Thanx.

Answer 1

Takes less than a second to spot. (If you had error reporting on it would take even less than that)
1) Your connection is mysqli but your query call is mysql
$result = mysql_query("SELECT id FROM members WHERE UserName = $valuetotest");
2) Value of $valuetotest is a string value and needs to be within quotes in your query. Should be like
SELECT id FROM members WHERE UserName = 'hellohi'
And not like
SELECT id FROM members WHERE UserName = hellohi
And Oh, How can I prevent SQL injection in PHP?

Answer 2

<?php
$result = mysqli_query("SELECT `id`, `Password` FROM `members` WHERE `UserName` = '$valuetotest'");
if(mysqli_num_rows($result) == 0)
{
echo "User not found";
}
$password = 'something2';
$userData = mysqli_fetch_array($result, MYSQL_ASSOC);
if($password != $userData['Password'])
{
echo "Password not found";
}else{ // Redirect to home page after successful login.
header('Location: welcome.php');
}
?>

Answer 3

You are selecting a text so you should use ' ' Symbols in your Select statement.
Like this:
$valuetotest = 'something';
$result = mysql_query("SELECT id FROM members WHERE UserName = '$valuetotest'");

Answer 4

$result = mysql_query("SELECT id FROM members WHERE UserName = '".$valuetotest."'");