Null Values in DB - php

Question

I am trying to make a VERY simple PHP form that posts a form to MySQL Database, however I am having some issues, and would welcome a simple fix for this if possible:
My PHP:
<?php
$con=mysqli_connect("serveraddress","db","password","dbname");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$sql="INSERT INTO Persons (email, type, cats)
VALUES
('$_POST[email]','$_POST[type]','$_POST[cats]')";
if (!mysqli_query($con,$sql))
{
die('Error: ' . mysqli_error($con));
}
echo "1 record added";
mysqli_close($con);
?>
My HTML:
<form action="personuploader.php" method="post">
<table class="#">
<tr>
<th colspan="2">Test</th>
</tr>
<tr>
<td>Email Address:</td>
<td><input type="text" name="email"> </td>
</tr>
<tr>
<td>Type:</td>
<td><input type="text" name="type"> </td>
</tr>
<tr>
<td>Cats:</td>
<td><input type="text" name="cats"> </td>
</tr>
<tr>
<td></td>
<td><input type="submit" value="upload" name="upload">
</tr>
</table>
</form>
My SQL Configuration:
Even though I have not null set in the DB I am getting empty results, is it possible to stop the form resubmitting on refresh causing null results be entered into the DB. I will enter some form validation to stop null results passing into the post script in the future but refreshing the page still sends over null results.

Answer 1

Edit:
Your column names have mixed-case letters (Cats and cats are not the same)
I edited my answer, where I changed it from:
$sql="INSERT INTO `Persons` (`email`, `type`, `cats`)
to
$sql="INSERT INTO `Persons` (`Email`, `Type`, `Cats`)
I also made a mistake with a missing ) for if(empty($_POST['email'] which has been fixed.
Please make sure also, that your column names are indeed called Email Type Cats and not email type cats Change it to the letter-case that is in your DB.
Your table's original structure: (larger image)
You should have talked to me first, instead of posting a new question with my code
See the rest below in the code.
As I stated in my comments under your original question, have put this together for you.
Don't use this method VALUES ('$_POST[email]','$_POST[type]','$_POST[cats]') you're open to SQL injection
To avoid re-submissions causing an empty entry, you can use a header() to redirect to another page, or use AJAX
However, I am sure there are other ways of doing this in the query itself, I just don't remember how right now.
I.e.: In place of where you have echo "1 record added";
you can do header("Location: added.php"); exit();
You can also use a conditional statement:
if(empty($_POST['variable'])){ die("Fill this in.");}
Try the following. It will check for empty fields, as well as check if the upload submit-type button is set.
Plus, I modified the way your query was done, replacing POST variables with mysqli_real_escape_string()
<?php
$con=mysqli_connect("serveraddress","db","password","dbname");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
if(isset($_POST['upload'])){
// You can replace the || with && if required
// depending on what you want to check for.
if(empty($_POST['email']) || empty($_POST['type']) || empty($_POST['cats']))
{
die("You need to fill in all the fields.");
}
$email = mysqli_real_escape_string($con, $_POST['email']);
$type = mysqli_real_escape_string($con, $_POST['type']);
$cats = mysqli_real_escape_string($con, $_POST['cats']);
$sql="INSERT INTO `Persons` (`Email`, `Type`, `Cats`)
VALUES ('$email','$type','$cats')";
if (!mysqli_query($con,$sql))
{
die('Error: ' . mysqli_error($con));
}
// Uncomment out if you're going to use echo, but not with header.
// echo "1 record added";
header("Location: redirect_to_other_page.php");
exit();
} // end of if(isset($_POST['upload']
// else conditional statement for if(isset($_POST['upload']
else{ echo "You cannot do this operation from here."; }
mysqli_close($con);
?>
Footnotes:
Just saying, the following:
('$_POST[email]','$_POST[type]','$_POST[cats]')
should have been:
('$_POST['email']','$_POST['type']','$_POST['cats']')
However, using this method is highly discouraged, as I already mentioned.

Answer 2

You need to check if a submit actually occured:
if ($_SERVER["REQUEST_METHOD"] == 'POST') {
... submit occured, do DB stuff
}
And note that an empty string is NOT the same as an SQL null. Empty string is just that - a string which happens to be empty/zero-length. An SQL null is quite literally "unknown". Your code cannot insert an actual null - it can only ever insert empty strings.

Answer 3

You should check whether the Upload button has been clicked on the "personuploader.php" file.
// Initializing Variables
$email = '';
$type = '';
$error = false;
if ( isset ( $_POST['upload'] ) ) {
// Then capture the POST Variables
$email = $_POST['email'];
// Do Some Validations
if ($email == '') {
$error = true;
}
// Process the Form if NO Errors
if ($error == false) {
// Insert The Data into DB
}
}