[SOLVED] need to check duplicated emails for email sign up form

[bradkenyon]

I have this code that adds email addresses to a table, and I want to check to see if the email address is already in the table, how would I go about that w/ the current code?

 

Any help is appreciated.

 

include('db.php');
if($_POST)
{
	$fname=$HTTP_POST_VARS['fname'];
	$lname=$HTTP_POST_VARS['lname'];
	$email=$HTTP_POST_VARS['email'];

	$query = mysql_query("INSERT INTO maillist (fname, lname, email) VALUES('$fname', '$lname', '$email')");

	result - mysql_query($query);
	if($result)
		echo mysql_affected_rows().' maillist inserted into database.';

?>		
	<h2 align="center">Thank You for signing up, you'll now receive festival updates!</h2>
<?
}
else
{
?>
	<span class="heading">Sign Up</span>
	<p>
	<form method="post" action="<?=$_SERVER["PHP_SELF"]?>">
	<table width="100%"  border="0" cellpadding="5" cellspacing="0" bgcolor="#CAD7BB">
	<tr>
		<td><strong>Email:</strong></td>
		<td><input type="text" name="email"></td>
	</tr>
	<tr>
		<td><strong>First Name:</strong></td>
		<td><input type="text" name="fname"></td>
	</tr>
	<tr>
		<td><strong>Last Name:</strong></td>
		<td><input type="text" name="lname"></td>
	</tr>
	<tr>
		<td colspan="2"><input type="Submit" name="Submit" value="Submit"></td>
	</tr>
	</table>
<?
}
?>

 

[ProblemHelpPlease]

Try this, it checks for an matching email address.

 

include('db.php');
if($_POST)
{
	$fname=$HTTP_POST_VARS['fname'];
	$lname=$HTTP_POST_VARS['lname'];
	$email=$HTTP_POST_VARS['email'];


$checktable = mysql_query("SELECT * FROM maillist WHERE email='$email' "); 

$nrows = mysql_num_rows($checktable);

if ($nrows == 0)

{
	$query = mysql_query("INSERT INTO maillist (fname, lname, email) VALUES('$fname', '$lname', '$email')");

	result - mysql_query($query);
	if($result)
		echo mysql_affected_rows().' maillist inserted into database.';



?>		
	<h2 align="center">Thank You for signing up, you'll now receive festival updates!</h2>
<?


}


}
else
{
?>
	<span class="heading">Sign Up</span>
	<p>
	<form method="post" action="<?=$_SERVER["PHP_SELF"]?>">
	<table width="100%"  border="0" cellpadding="5" cellspacing="0" bgcolor="#CAD7BB">
	<tr>
		<td><strong>Email:</strong></td>
		<td><input type="text" name="email"></td>
	</tr>
	<tr>
		<td><strong>First Name:</strong></td>
		<td><input type="text" name="fname"></td>
	</tr>
	<tr>
		<td><strong>Last Name:</strong></td>
		<td><input type="text" name="lname"></td>
	</tr>
	<tr>
		<td colspan="2"><input type="Submit" name="Submit" value="Submit"></td>
	</tr>
	</table>
<?
}
?>

[akitchin]

it is much faster to use COUNT(), although problemHelpPlease's solution should still work:

 

$nrows = mysql_result(mysql_query("SELECT COUNT(*) FROM maillist WHERE email='$email'"), 0, 0);

 

keep in mind this won't play well if you end up with a query error of any kind.

[discomatt]

Rather than perform two queries, I like to make the column 'unique' in MySQL... you can then check mysql_error() for the string 'Duplicate entry' -> If it's there, you know that the email is already taken.

 

I'm also an efficiency freak, though

[akitchin]

making the column a unique key is also a good way to add a last line of defense against duplicate entries.  i would argue that queries are never the bottleneck in small systems (vs. doing a string search), but i don't think it's really relevant - disco's right, you could do it with one query alone.

[bradkenyon]

thanks guy, did the trick!