ISSET Php mysql [duplicate] - php

Question

This question already has answers here:
isset() function is returning true even when item is not set
(4 answers)
Closed 9 years ago.
guys how come whenever i click submit button on my form without any data in the textbox, it's saying echo 'Either your username, or email is already taken!'; . How come it still passes through this despite of the form not having any data? what could be the best explanation?
if(isset($_POST['username']) && isset($_POST['email']))
{
$username = $_POST['username'];
$email = $_POST['email'];
$extract= mysql_query("SELECT * FROM users where username='$username'");
$resultq = mysql_num_rows($extract);
if($resultq > 0)
{
echo 'Either your username, or email is already taken!';
return;
}
}
Please hi'm stuck with this line for 12 hours, i can't seem to move on :(

Answer 1

isset renders true for empty string. it checks the existence of a variable. Here is a detailed explanation.
You should use if (trim($_POST['username']) != "")

Answer 2

if(isset($_POST['submit']))
{
$username = $_POST['username'];
$email = $_POST['email'];
$extract= mysql_query("SELECT * FROM users where username='$username'");
$resultq = mysql_num_rows($extract);
if($resultq > 0)
{
echo 'Either your username, or email is already taken!';
return;
}
}

Answer 3

You can also try !empty :
If you want to check both username OR email if already exist you also need to check email in select query
if(!empty($_POST['username']) && !empty($_POST['email']))
{
$username = $_POST['username'];
$email = $_POST['email'];
$extract= mysql_query("SELECT * FROM users where username='$username' OR email='$email'");
$resultq = mysql_num_rows($extract);
if($resultq > 0)
{
echo 'Either your username, or email is already taken!';
return false;
}
else
{
echo 'Accept';
return true;
}
}