How to check if user already exist? - php

Question

class Users {
public $username = null;
public $password = null;
public $salt = "Zo4rU5Z1YyKJAASY0PT6EUg7BBYdlEhPaNLuxAwU8lqu1ElzHv0Ri7EM6irpx5w";
public function __construct( $data = array() ) {
if( isset( $data['username'] ) ) $this->username = stripslashes( strip_tags( >$data['username'] ) );
if( isset( $data['password'] ) ) $this->password = stripslashes( strip_tags( >$data['password'] ) );
}
}
public function storeFormValues( $params ) {
$this->__construct( $params );
}
public function register() {
$correct = false;
try {
$con = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$con->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
$sql = "INSERT INTO users(username, password) VALUES(:username, :password)";
$stmt = $con->prepare( $sql );
$stmt->bindValue( "username", $this->username, PDO::PARAM_STR );
$stmt->bindValue( "password", hash("sha256", $this->password . $this->salt), PDO::PARAM_STR );
$stmt->execute();
return "Registration Successful <br/> <a href='index.php'>Login Now</a>";
}catch( PDOException $e ) {
return $e->getMessage();
}
}
}
I would like to check if a user already exist in my database, because it lets me create accounts with same username anytime.
Thanks.

Answer 1

I would recommend a few things to help here.
1) Make your username column unique in the database. This would prevent usernames that are not unique from being inserted.
2) Once you have a unique index on username, attempt the insert, and check for success on the insert. Since you can get the error code from mysql, if the query was not successful and the error code is due to a duplicate value...throw the username already exists error.

Answer 2

This is the basic idea of how to return if the username exists.
public function username($username)
{
$sth = $this->db->prepare("SELECT id, username FROM table WHERE username = ?");
$sth->execute(array($username));
$row = $sth->fetch();
if(username == $row['username'])
{
do code here since username does not exist
} else {
echo 'username already exists';
}
}

Answer 3

$sell= mysql_query("select * from `signup` where emailid='$email'");
$cntc=mysql_num_rows($sell);
if($cntc==0) {
$sql=mysql_query("INSERT INTO `signup`(`firstname`,`lastname`,`emailid`,`dob`,`companyname`,`phoneno`,`password`) VALUES ('$name','$lastname','$email','$dob','$comname','$phone','$pass')");
if($sql) {
echo'inserted successfully';
}
} else {
echo'Email is already exist. ';
}