Duplicate values entering into database on input - php

Question

I'm new to web development and managed to create a form which collects data but discovered that there are some duplicate values that manage to enter the database on submit. Any ideas on how to maintain that data is captured only once into the database? Below is my code that posts details of form on submit.
<?php include 'database.php';?>
<?php
$customer_name = data_input($_POST["customer_name"]);
$customer_gender = data_input($_POST["customer_gender"]);
$mobile_number = data_input($_POST["mobile_number"]);
$unique_box_id = data_input($_POST["unique_box_id"]);
$casn_number = data_input($_POST["casn_number"]);
$customer_address = data_input($_POST["customer_address"]);
$dso_region = data_input($_POST["dso_regions"]);
$state = data_input($_POST["state"]);
$decoder_type = data_input($_POST["decoder_type"]);
$antennae_type = data_input($_POST["antennae_type"]);
$brand_of_box = data_input($_POST["brand_of_box"]);
$call_category = data_input($_POST["call_category"]);
$complaint_category = data_input($_POST["complaint_category"]);
$agent_notes = data_input($_POST["agent_notes"]);
$resolution = data_input($_POST["resolution"]);
$agent_name = data_input($_POST["agent_name"]);
function data_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
mysqli_query($connect,"INSERT INTO customer_details (NAMES, GENDER,MOBILE_NUMBER,UNIQUE_BOX_ID,CASN_NUMBER,
CUSTOMER_ADDRESS,DSO_REGION,STATE,DECODER_TYPE,ANTENNAE_TYPE,BRAND_OF_BOX,
CALL_CATEGORY,COMPLAINT_CATEGORY,AGENT_NOTES,RESOLUTION,AGENT_NAME)
VALUES ('$customer_name', '$customer_gender', '$mobile_number','$unique_box_id','$casn_number','$customer_address','$dso_region','$state','$decoder_type',
'$antennae_type','$brand_of_box','$call_category','$complaint_category','$agent_notes','$resolution','$agent_name')");
if (mysqli_affected_rows($connect)> 0){
echo "<p>Customer Details submitted</p>";
//echo "Go Back";
header("Location: {$_SERVER['HTTP_REFERER']}");
exit;
} else {
echo "Customer Details NOT submitted<br />";
echo mysqli_error ($connect);
}
mysql_close($connnet)
?>

Answer 1

I think your if condition is wrong, you are checking on connection variable
But you should check another variable, like this
$insertQuert = mysqli_query($connect,"INSERT INTO ...
then in if condition
if (mysqli_affected_rows($insertQuery)> 0){