How to check if username already exist using PDO? - php

Question

am currently working on a project and i have the script for insertion.my table is called survey and the fields are id,username,password,province. the username is set to unique key. the insertion process is working fine without any duplicate entry but when i try to insert a duplicate entry at always shows me this error
SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'bluff' for key 'username'
I know what this error mean, my problem is that how can i can if username already exist or not i want an alert message to pop up..
here is my code
class.user.php
public function username($username){
$stmt = $this->db->prepare("SELECT count(*) FROM tish_images WHERE username = :username");
$stmt->execute(array($username));
$number_of_rows = $result->fetchColumn();
if($number_of_rows >= 1) {
echo 'username does exist'; // or return so you get the value
} else {
echo 'username does not exist'; //also return?
}
}
public function create($username,$password,$province)
{
try
{
$stmt = $this->db->prepare("INSERT INTO tish_images(username,password,province) VALUES(:username, :password, :province)");
$stmt->bindparam(":username",$username);
$stmt->bindparam(":password",$password);
$stmt->bindparam(":province",$province);
$stmt->execute();
return true;
}
catch(PDOException $e)
{
echo $e->getMessage();
return false;
}
}
index.php
<?php
include_once 'DB.php';
$username = isset($_GET['username']) ? $_GET['username'] : '';
$password = isset($_GET['password']) ? $_GET['password'] : '';
$province = isset($_GET['province']) ? $_GET['province'] : '';
if(isset($_FILES['files'])){
$id = $_GET['id'];
$username = $_POST['username'];
$password = $_POST['password'];
$province = $_POST['province'];
if($crud->upload($id,$FILE_NAME,$FILE_SIZE,$FILE_TYPE,$username,$password,$province))
{
echo "<script type='text/javascript'>alert('Successfully Updated!');</script>";
}
else
{
echo "<script type='text/javascript'>alert('Updating Failed!');</script>";
}
}
if(isset($_GET['id']))
{
$id = $_GET['id'];
extract($crud->getID($id));
}

Answer 1

You should run a SELECT before performing the query to see if the username exists.
// count how many rows with user name exists
$checkUserStmt = $this->db->prepare("
SELECT count(1)
FROM tish_images
WHERE username = :username
");
$checkUserStmt->execute(array(":username" => $username));
// fetch the count result
if ($checkUserStmt->fetchColumn() > 0) {
// username already exists
} else {
// username available
} //if
A few notes.
You still might get a duplicate entry error if you have two users trying to register the same username at close interval.
You should hash the password see Secure hash and salt for PHP passwords

Answer 2

To check if username or email already exists. I added email in there as this is also useful. You don't want two users with the same email address. Well I wouldn't see the need for it. :)
Complete code added and up to date.
$query_check_user_name = $this->db_connection->prepare('SELECT user_name, user_email FROM users WHERE user_name=:user_name OR user_email=:user_email');
$query_check_user_name->bindValue(':user_name', $user_name, PDO::PARAM_STR);
$query_check_user_name->bindValue(':user_email', $user_email, PDO::PARAM_STR);
$query_check_user_name->execute();
$result = $query_check_user_name->fetchAll();
if ($result > 0) {
echo "Someone with that username/email already exists.";
} else {
//Continue with proccessing the form
}
OR
$query_check_user_name = $this->db_connection->prepare('SELECT user_name, user_email FROM users WHERE user_name=:user_name OR user_email=:user_email');
$query_check_user_name->bindValue(':user_name', $user_name, PDO::PARAM_STR);
$query_check_user_name->bindValue(':user_email', $user_email, PDO::PARAM_STR);
$query_check_user_name->execute();
$result = $query_check_user_name->fetchAll();
if ($result > 0) {
return true;
} else {
return false;
}