Why is my PHP / SQL generating duplicate database entries? - php

Question

I'm quite new to PHP and an absolute beginner when it comes to SQL. I'm just learning the basics and I can't get my head around why my code is generating a duplicate entry every time the form is submitted, e.g.
Name: Joe Blogs Email: info#email.co.uk
Name: Joe Blogs Email: info#email.co.uk
The database has a table called user and two columns, name and email.
My index file looks like this, it has a simple form for name and email, and inserts the data on submit:
<form method="post" action="insert.php">
<input name="name" type="text">
<input name="email" type="email">
<input type="submit" value="Submit Form">
</form>
<?php
$servername = "localhost";
$username = "DB_USER";
$password = "PASSWORD";
$dbname = "DB_NAME";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sqlout = "SELECT name, email FROM user";
$result = $conn->query($sqlout);
if ($result->num_rows > 0) {
// output data of each row
while($row = $result->fetch_assoc()) {
echo "<b>Name:</b> " . $row["name"]. " <b>Email:</b> " . $row["email"]. "<br>";
}
} else {
echo "0 results";
}
$conn->close();
?>
<form method="post" action="wipe.php">
<input type="submit" value="Wipe ALL Data">
</form>
This insert.php file is called when the form is submitted:
<?php
$servername = "localhost";
$username = "DB_USER";
$password = "PASSWORD";
$dbname = "DB_NAME";
// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = "INSERT INTO user ( name, email ) VALUES ( '{$conn->real_escape_string($_POST['name'])}', '{$conn->real_escape_string($_POST['email'])}' )";
$insert = $conn->query($sql);
if ($conn->query($sql) === TRUE) {
echo "New record created successfully";
} else {
echo "Error: " . $sql . "<br>" . $conn->error;
}
$conn->close();
?>
Back
I've probably made some basic mistakes but I'm not sure why it is adding duplicates. Is it something to do with connecting twice to the database in each file? Is there a better way to connect only once? Or is it caused by the form submission itself?

Answer 1

Because you call query twice:
$insert = $conn->query($sql);
if ($conn->query($sql) === TRUE) {
You should rewrite is as
$insert = $conn->query($sql);
if ($insert === TRUE) {
Also, you should really be using prepared statements.

Answer 2

Your code Call $conn->query twice
$insert = $conn->query($sql);// first time
if ($conn->query($sql) === TRUE) {// second time

Answer 3

if ($insert === TRUE) {
echo "New record created successfully";
} else {
echo "Error: " . $sql . "<br>" . $conn->error;
}

Answer 4

You need change:
$sql = "INSERT INTO user ( name, email ) VALUES ( '{$conn->real_escape_string($_POST['name'])}', '{$conn->real_escape_string($_POST['email'])}' )";
$insert = $conn->query($sql);
if ($conn->query($sql) === TRUE) {
echo "New record created successfully";
} else {
echo "Error: " . $sql . "<br>" . $conn->error;
}
to
$sql = "INSERT INTO user ( name, email ) VALUES ( '{$conn->real_escape_string($_POST['name'])}', '{$conn->real_escape_string($_POST['email'])}' )";
$status = $conn->query($sql);
if ($status === TRUE) {
echo "New record created successfully";
} else {
echo "Error: " . $sql . "<br>" . $conn->error;
}