A query may fail for various reasons in which case both the mysql_* and the mysqli extension will return false
from their respective query functions/methods. You need to test for that error condition and handle it accordingly.
NOTE The mysql_ functions are deprecated and have been removed in php version 7.
Check $result
before passing it to mysql_fetch_array
. You’ll find that it’s false
because the query failed. See the [mysql_query
][1] documentation for possible return values and suggestions for how to deal with them.
$username = mysql_real_escape_string($_POST['username']);
$password = $_POST['password'];
$result = mysql_query("SELECT * FROM Users WHERE UserName LIKE '$username'");
if($result === FALSE) {
trigger_error(mysql_error(), E_USER_ERROR);
}
while($row = mysql_fetch_array($result))
{
echo $row['FirstName'];
}