Checking if username exists in DB with PHP and MySQL [duplicate] - php

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Closed 1 year ago.
Been struggling with this for a few days, and read a ton of similar problems but still haven't been able to figure it out. I am trying to take user information via an html form and update my database with it, but only if the username doesn't already exist...
Issue 1: No matter what, it can keep creating entries with the same username
Issue 2: I keep getting the error Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, bool given
I am sure they are connected but for the life of me I can't figure out what the fix is.
<?php
//declare variables
$dbhost = "localhost";
$dbuser = "root";
$dbpass = "mypassword";
$db = "user_info";
if (!empty($_POST)) {
//connect to mysqli
$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $db);
//check connection
if ($mysqli->connect_error) {
die('Connect Error: ' . $mysqli->connect_errno . ': ' . $mysqli->connect_error );
}
//declare user variables
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$user_name = $_POST['user_name'];
$pass = $_POST['pass'];
$address = $_POST['address'];
$phone = $_POST['phone'];
//get data from form
$sql = "INSERT INTO users (first_name, last_name, user_name, pass, address, phone) VALUES
('{$mysqli->real_escape_string($first_name)}',
'{$mysqli->real_escape_string($last_name)}',
'{$mysqli->real_escape_string($user_name)}',
'{$mysqli->real_escape_string($pass)}',
'{$mysqli->real_escape_string($address)}',
'{$mysqli->real_escape_string($phone)}')";
// ** HERE IS WHERE I AM HAVING ISSUES **
//query to see if entered username already exists
$result = $mysqli->query("SELECT * FROM users WHERE user_name =$user_name");
//alert if user name taken
if (mysqli_num_rows($result) > 0) {
echo "<b>Username already taken! Please select another.</b>";
} else {
//continue to insert into database if username is unique
$insert = $mysqli->query($sql);
//print response from mysql
if ($insert) {
echo "Success! Row ID: {$mysqli->insert_id}";
} else {
die("error: {$mysqli->errno}");
}
}
//close our app
$mysqli->close();
}
?>

Answer 1

Try like this
<?php
if (!empty($_POST)) {
//connect to mysqli
$mysqli = new mysqli($dbhost, $dbuser, $dbpass, $db);
//check connection
if ($mysqli->connect_error) {
die('Connect Error: ' . $mysqli->connect_errno . ': ' . $mysqli->connect_error );
}
//declare user variables
$first_name = $_POST['first_name'];
$last_name = $_POST['last_name'];
$user_name = $_POST['user_name'];
$pass = $_POST['pass'];
$address = $_POST['address'];
$phone = $_POST['phone'];
$query = $mysqli->prepare("SELECT count(*) FROM users WHERE user_name = ?");
$query->bind_param('s', $user_name);
$query->bind_result($cnt);
$query->execute();
$query->store_result();
$query->fetch();
$query->close();
if ($cnt > 0) {
echo "<b>Username already taken! Please select another.</b>";
} else {
$query = $mysqli->prepare("INSERT INTO users (first_name, last_name, user_name, pass, address, phone) VALUES (?,?,?,?,?,?)");
$query->bind_param('ssssss', $first_name, $last_name, $user_name, $pass, $address, $phone);
$query->execute();
if ($query->execute()) {
echo "Success! Row ID: {$query->insert_id}";
} else {
die("error: {$query->errno}");
}
$query->close();
}
}