How to authenticate users with credentials in MySQL database - php

Question

On my form page, I have two textboxes with the names name and password.
When the user hits submit, it sends that data into two columns in a MySQL database named 'name' and 'password'.
After the data is recorded (which is the part I understand and don't need help with), I want the user to be at the sign-in page and type in his/her name and password and only be allowed into the site if the name and password data already exist in the database (part that I don't understand).
Would I use the following query :
SELECT * FROM tablename WHERE name & password = "'$_POST[name]', $_POST[password]'

Answer 1

You should use AND or && instead of just a single ampersand (&), and separate the variables to be binded accordingly to their column name.
You should also consider sanitizing your variables before using them to your queries. You can use *_real_escape_string() to prevent SQL injections.
$name = mysql_real_escape_string($_POST["name"]);
$password = mysql_real_escape_string($_POST["password"]);
"SELECT * FROM tablename WHERE name = '".$name."' AND password = '".$password."'"
But the best recommendation that I can give to you is to use prepared statement rather than the deprecated mysql_*
if($stmt = $con->prepare("SELECT * FROM tablename WHERE name = ? AND password = ?")){ /* PREPARE THE QUERY; $con SHOULD BE ESTABLISHED FIRST USING ALSO mysqli */
$stmt->bind_param("ss",$_POST["name"],$_POST["password"]); /* BIND THESE VARIABLES TO YOUR QUERY; s STANDS FOR STRINGS */
$stmt->execute(); /* EXECUTE THE QUERY */
$noofrows = $stmt->num_rows; /* STORE THE NUMBER OF ROW RESULTS */
$stmt->close(); /* CLOSE THE STATEMENT */
} /* CLOSE THE PREPARED STATEMENT */
For securing password, you could also look at password_hash().

Answer 2

Please Always use Prepared statement to execute SQL code with Variable coming from outside your code. Concatenating variable from user input into SQL code is dangerous ( consider SQL injection ), you could use prepared statement with mysqli or PDO ( recommended ).
Mysqli example:
$mysqli = new mysqli("example.com", "user", "password", "database");
// error check you connection here
$query='select * from tablename where user =? AND password=?';
$stmt = $mysqli->prepare($query);
$stmt->bind_param("ss", $user,$password);
$stmt->execute();
if($stmt->num_rows!=1) {
// check failed
}else{
// check success
}
PDO example (recommended )
$dbh = new PDO('mysql:host=localhost;dbname=test', $user, $pass);
// error check you connection here
$query='select * from tablename where user =? AND password=?';
$stmt = $dbh->prepare($query);
$stmt->bindParam(1,$user);
$stmt->bindParam(2,$password);
$stmt->execute();
if($sth->fetchAll()) {
// check success
}else{
// check failure
}
Additionally you should also consider using some form of 1-way password encryption ( password hashing ) before storing it in your database and compare it to the hash( the most accepted way to do it is using Bcrypt).

Answer 3

You can use something like
SELECT count(*) FROM tablename WHERE name = "'.$_POST[name].' AND password = "'. $_POST[password].'"
You should expect count to be exactly 1 - indicating valid user, 0 - indicating invalid user
Anything greater than 1 should be invalid scenario indicating some kind of inconsistency in your database...

Answer 4

You should assign the variables to name & pass subsequently.
You can try this:
$con = mysqli_connect("localhost","YOURUSER","YOURPASS","YOURDB");
if (mysqli_connect_errno())
{
echo"The Connection was not established" . mysqli_connect_error();
$user
= mysqli_real_escape_string($con,$_POST['user']);
$pass = mysqli_real_escape_string($con,$_POST['password']);
$query = "select * from tablename where user ='$user' AND password='$pass' ";
$run = mysqli_query($con,$query);
$check = mysqli_num_rows($run );
if($check == 0)
{
echo "<script> alert('Password or Email is wrong,try again!')</script>";
}
else
{
//get a session for user
$_SESSION['user']=$user;
// head to index.php; you can just put index.php if you like
echo"<script>window.open('index.php?login=Welcome to Admin Area!','_self')</script>";
}