where condition in select query - php

Question

I have to check both the user name and the email if any of the two already exist,
When I add OR in where condition It is always going in IF condition.
Code:
$fetch_user=mysql_query("SELECT userid FROM users WHERE username ='".$username."' OR email='".$email."'") or die(mysql_error());
if(mysql_num_rows($fetch_user))
{
echo '<font color="red">The nickname <strong>'.$username.''.$email.'</strong>'.' is already in use.</font>';
}
else
{
$query = mysql_query("insert into users values ('','$username','$email','$password','','$roll')") or die(mysql_error());
if($query)
{
echo 'Successfully Inserted';
}
else
{
echo 'Insertion Faild';
}
}
Thanks for any help!

Answer 1

I do not see any thing wrong in the code. However i can only see the logic is incorrect. If username or email already exists, you are showing a message that nickname username and email already in use. It may be possible that only username is already in use but not the email and vice versa. So you need to show proper message to the user which one is taken and which one not.
<?php
$userNameTaken = false;
$emailTaken = false;
//check if username exists
$checkUsername = mysql_query("SELECT userid FROM users WHERE username ='".$username."'") or die(mysql_error());
if(mysql_num_rows($checkUsername))
{
$userNameTaken = true;
}
//check if email exists
$checkEmail = mysql_query("SELECT userid FROM users WHERE email ='".$email."'") or die(mysql_error());
if(mysql_num_rows($checkEmail))
{
$emailTaken = true;
}
if($userNameTaken || $emailTaken) //if any of username or email taken
{
if($userNameTaken && $emailTaken) //username and email both taken
{
echo '<font color="red">The username <strong>'.$username.'</strong> and email <strong>'.$email.'</strong> already in use.</font>';
}
else if($userNameTaken && !$emailTaken) //only username taken
{
echo '<font color="red">The username <strong>'.$username.'</strong> is already in use.</font>';
}
else if(!$userNameTaken && $emailTaken) //only email taken
{
echo '<font color="red">The email <strong>'.$email.'</strong> is already in use.</font>';
}
}
else
{
$query = mysql_query("insert into users values ('','$username','$email','$password','','$roll')") or die(mysql_error());
if($query)
{
echo 'Successfully Inserted';
}
else
{
echo 'Insertion Faild';
}
}
?>

Answer 2

Only change condition
$fetch_user=mysql_query("SELECT userid FROM users WHERE username ='".$username."' OR email='".$email."'") or die(mysql_error());
$num = mysql_num_rows($fetch_user);
if($num > 1)
{
echo '<font color="red">The nickname <strong>'.$username.''.$email.'</strong>'.' is already in use.</font>';
}
else
{
$query = mysql_query("insert into users values ('','$username','$email','$password','','$roll')") or die(mysql_error());
if($query)
{
echo 'Successfully Inserted';
}
else
{
echo 'Insertion Faild';
}
}

Answer 3

You are not validating the result from teh sql query .
the following code will work
$fetch_user=mysql_query("SELECT userid FROM users WHERE username ='".$username."' OR email='".$email."'") or die(mysql_error());
if( !$fetch_user)
{
if(mysql_num_rows($fetch_user) > 0 )
{
echo '<font color="red">The nickname <strong>'.$username.''.$email.'</strong>'.' is already in use.</font>';
}
else
{
$query = mysql_query("insert into users values ('','$username','$email','$password','','$roll')") or die(mysql_error());
if($query)
{
echo 'Successfully Inserted';
}
else
{
echo 'Insertion Faild';
}
}
}
else
[
echo 'query failed';
}
Also look the following documentation links so you understand the functionalities better
http://php.net/manual/en/function.mysql-num-rows.php
http://php.net/manual/en/function.mysql-query.php