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@NogDogAug 05.2009 — #Note that if you do not use transactions and lock that table during your script, it's possible for two concurrent scripts to still end up with the same user name.
You can avoid this by using transactions. Or, you can simply make sure the column has a unique index assigned, then just do your insert query; and if you get an duplicate key error (error 1062 in MySQL) you know you have a duplicate user name and ask the user to try something else.
Registration Form – Checking For the Same Username
Hey everyone. I have a registration form. It work perfectly, but I don’t want 2 users with the same username. lol Anyways, how would I do a check to see if the username field is the same as an already taken username, and display a message to show that the username is already taken? Thanks! Here’s the code:
[code=php]<?php
mysql_connect(‘…’, ‘…’, ‘…’) or die(mysql_error());
mysql_select_db (“…”) or die(mysql_error());
if (clean($_GET[‘register’] == ‘true’)) {
registerUser();
}
//Function to sanitize values received from the form. Prevents SQL injection
function clean($str) {
$str = @trim($str);
if(get_magic_quotes_gpc()) {
$str = stripslashes($str);
}
return mysql_real_escape_string($str);
}
function registerUser() {
$username = clean($_POST[‘username’]);
$firstname = clean($_POST[‘firstname’]);
$lastname = clean($_POST[‘lastname’]);
$password = md5( clean($_POST[‘password’]));
$email = clean($_POST[’email’]);
$acename1 = clean($_POST[‘acename1’]);
$acename2 = clean($_POST[‘acename2’]);
$acename3 = clean($_POST[‘acename3’]);
$acename4 = clean($_POST[‘acename4’]);
$acecity1 = clean($_POST[‘acecity1’]);
$acecity2 = clean($_POST[‘acecity2’]);
$acecity3 = clean($_POST[‘acecity3’]);
$acecity4 = clean($_POST[‘acecity4’]);
$gender = clean($_POST[‘gender’]);
$sql = “INSERT INTO users (username, firstname, lastname, password, email, acename1, acename2, acename3, acename4, acecity1, acecity2, acecity3, acecity4, gender) VALUES (‘$username’, ‘$firstname’, ‘$lastname’, ‘$password’, ‘$email’, ‘$acename1’, ‘$acename2’, ‘$acename3’, ‘$acename4’, ‘$acecity1’, ‘$acecity2’, ‘$acecity3’, ‘$acecity4’, ‘$gender’)”;
mysql_query($sql) or die(Mysql_error());
echo “<script type=’text/javascript’>alert(‘Registration successful! Please login in the menu at left.’)</script>”;
}
?>
<html>
<head>
<title>ACE Online Community</title>
<link href=”styles.css” rel=”stylesheet” type=”text/css”>
<script type=”text/javascript”>
function validateFormOnSubmit(theForm) {
var reason = “”;
reason += validateUsername(theForm.username);
reason += validatePassword(theForm.password);
reason += validateEmail(theForm.email);
reason += validatePhone(theForm.phone);
reason += validateEmpty(theForm.from);
if (reason != “”) {
alert(“Some fields need correction:n” + reason);
return false;
}
return true;
}
function validateEmpty(fld) {
var error = “”;
if (fld.value.length == 0) {
fld.style.background = ‘Yellow’;
error = “The required field has not been filled in.n”
} else {
fld.style.background = ‘White’;
}
return error;
}
</script>
</head>
<body bgcolor=”black” link=”red” alink=”red” vlink=”red”>
<font color=”silver”>
<center><h2>ACE Online Community</h2></center>
<?php include(“menu.php”); ?>
<?php include(“registerform.php”); ?>
</font>
</body>
</html>
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@NogDogAug 05.2009 — #Note that if you do not use transactions and lock that table during your script, it's possible for two concurrent scripts to still end up with the same user name.- [list=1]
You can avoid this by using transactions. Or, you can simply make sure the column has a unique index assigned, then just do your insert query; and if you get an duplicate key error (error 1062 in MySQL) you know you have a duplicate user name and ask the user to try something else.