PHP MySQL unable to jump to row 0 - php

Question

I recently started studying webdevelopment and for the first project we have to make a very simple login and registration function. now I got somewhere but suddenly I started getting this error.
Unable to jump to row 0 on MySQL result index 4.
This is the code where I get the error.
$conn = mysql_connect($servername, $username, $password, $database) or die("!Server");
if(!$conn){
die("Connection error: " . mysql_error());
}else{
echo "connection made";
}
$select_db= mysql_select_db($database, $conn);
if(!$select_db){
die("Database selection failed:: " . mysql_error());
}else{
echo "database selected";
}
$login_user = $_GET['username'];
$select_password = "SELECT `password` FROM `members` WHERE `username` = '$login_user'";
$result = mysql_query($select_password);
if(!$result){
die("Could not fetch the data " . mysql_error());
}
$password = mysql_result($result, 0);
echo $password;
I know there are other posts asking the same question but none of them where really helpful.
hope someone is able to help me.
Thanks for reading :)

Answer 1

It is possible that this row:
password = mysql_result($result, 0);
Cannot get rows when it does not match anything which is why you get the error.
Try instead:
if( $password = mysql_fetch_assoc($result) ) {
echo $password['password'];
} else {
echo 'no match';
}
See if that helps.
However, you really should move from mysql_* to PDO or mysqli.

Answer 2

I suggest to work with PDO, instead of mysql_... functions.
Not only because it's newer and object oriented but also because mysql... is deprecated.
So my answer is with PDO
From your code example I assume you have variables of servername, database, username & password. So to connect with PDO will look like this:
$con = new PDO("mysql:host=$servername;dbname=$database", $username, $password);
Then you can take your $_GET parameter using filter_input, which is also more suggested. Simple assignment look like this:
$login_user = filter_input(INPUT_GET,'username');
and then to run & fetch query like this:
$result_query = $con->query("SELECT `password` FROM `members` WHERE `username` = '$login_user'");
$result = $result_query->fetch(PDO::FETCH_ASSOC);
Now $result is an associative array, so to get password just use:
echo $result['password'];

Answer 3

Thanks alot for the help :) out of these answers I got everything I needed and now I am also going to switch to PDO for the final release though I am gonna stay with MySQL for now since I have to turn it in by monday.
Thanks alot :)

Answer 4

Change this:
$select_password = "SELECT `password` FROM `members` WHERE `username` = '$login_user'";
Into this:
$select_password = "SELECT password FROM members WHERE username = '$login_user'";