Php form submit and page redirect - php

Question

I am trying to redirect a to a new php page after the user has clicked on the submit button. I have got it to successfully send the form information to the MySQL database but then I cannot get a successful redirect.
I then changed some code and got it to successfully redirect but not send the form information to the database. My other php file is named nextForm.php and I have tried replacing the action="$_SERVER[PHP_SELF]" with the path to the nextForm.php file and I have tried using a require nextForm.php; line in the code where I want to redirect.
Here is the code I have currently:
<?php
//establish a connection to the MySQL db or terminate if ther is an error
$conn = mysqli_connect("localhost","root","mysql","covid_tech",3306) or die(mysqli_connect_error());
//HTML form to prompt user input
print <<<_HTML_
<FORM style="text-align:center" method="POST" action="$_SERVER[PHP_SELF]">
<div class="Customer_Name">
Enter Customer Name: <input type="text" name="Customer_Name" class="textbox">
</div>
<br/>
<div class="Contact_Name">
Enter Contact Name: <input type="text" name="Contact_Name" class="textbox">
</div>
<br/>
<div class="Contact_Phone">
Enter Contact Phone Number: <input type="text" name="Contact_Number" class="textbox">
<br/>
</div>
<button class="btn btn-1" style="text-align:center" onclick='disappear(this)' name="name_submit" method="POST" type="submit" value="find_cusName"><span>Enter Customer Name</span></button>
</FORM>
_HTML_;
//check to make sure the POST request was sent and check to make sure that there is a vlaue in the System POST variable
if($_SERVER['REQUEST_METHOD'] == "POST" and isset($_POST['Customer_Name'])){
//SQL string to find the name that was input on the page
$find_name_sql = "SELECT cusName,cusID from customer where cusName = '$_POST[Customer_Name]'";
//run the query on the db
$result_find_name = mysqli_query($conn, $find_name_sql);
//Check to see if the query returned any rows
if(mysqli_num_rows($result_find_name) > 0){
//If it did, it should only be 1 row and we fetch it
$row = mysqli_fetch_row($result_find_name);
//set our current_id variable to the value in $row[1] which is the cusID attribute from the db
$current_id = $row[1];
}
else{
//sql statment to insert a new customer into the customer table of the db
$insert_first_customer = "INSERT INTO customer (cusName,contactName,contactNo) values('$_POST[Customer_Name]','$_POST[Contact_Name]','$_POST[Contact_Number]')";
//run the insert query
$add = mysqli_query($conn,$insert_first_customer);
}
//redirect to next form page here
}
mysqli_close($conn);
?>

Answer 1

The action attribute simply works as a way to direct your GET/POST requests. If you would like to redirect after running your PHP code, you should use the header() function or use a meta tag.
Example:
header('Location:'.$_SERVER['SERVER_NAME'].'/nextForm.php');
or
echo '<meta http-equiv="refresh" content="0;url=nextForm.php">';
and finish your code with the exit() function so an attacker could not bypass your redirect.