if user_name is already registered, redirect back to the same page ex. register.php?q=user_exists

debugcn Published at Dev

Vivek Pandey

this the php part

<?php
include 'assets/db.php';

if(isset($_POST["register"])){

    $sql = "INSERT INTO table (name, email, user_name, pass) 

           VALUES ('".mysqli_real_escape_string($conn, $_POST["name"])."',
                   '".mysqli_real_escape_string($conn, $_POST["email"])."', 
                   '".mysqli_real_escape_string($conn, $_POST["user_name"])."', 
                   '".mysqli_real_escape_string($conn, $_POST["pass"])."')";

if ($conn->query($sql) === TRUE) {
    echo "<script type='text/javascript'>window.top.location='_sign_in.php?l=1';</script>";
} else {
    echo "<script type= 'text/javascript'>alert('Error! Please refresh the page and try again.');</script>";
}
$conn->close();

i am trying to avoid re-registration of any user_name, if user_name is already registered, redirect back to some page example- register.php?q=user_exists.

Geoffrey

To avoid duplicate user names, add a unique index to the table:

ALTER TABLE `table` ADD UNIQUE(`user_name`)

This will cause the insert to fail allowing you to detect the failure without needing an additional SELECT to check for a duplicate.

If you want to ensure the error is due to a duplicate value, check for mysql error 1062

Error: 1062 SQLSTATE: 23000 (ER_DUP_ENTRY)

You can check for this by using mysqli::errno and then redirect by simply sending the Location header, ie:

if (!$conn->query($sql))
{
  if ($conn->errno == 1062)
  {
    header("Location: register.php?q=user_exists");
    die();
  }

  die('Critical Failure');
}

Edit: Instead of just down voting, how about commenting on what is wrong with this answer?

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