Change signup page echo message based on if statement from different page - php

Question

I am practicing PHP and database creation and would like to change my message based on errors from the input. I can't figure out how to pass the changed messaged back and would appreciate any help given.
This is my sign up page
<main>
<h1>Signup<h1>
<h3>
<?php
echo $errorMsg;
?>
<h3>
<form action="includes/signup.inc.php" method="post">
<input type="text" name="uid" placeholder="Username">
<input type="text" name="mail" placeholder="E-mail">
<input type="password" name="pwd" placeholder="Password">
<input type="password" name="pwd_repeat" placeholder="Repeat Password">
<button type="submit" name="signup-submit">Submit</button>
<form>
</main>
This is my processing page
if(isset($_POST['signup-submit'])){
require 'dbh.inc.php';
$Name = $_POST['uid'];
$Email= $_POST['mail'];
$Password = $_POST['pwd'];
$PasswordRepeat = $_POST['pwd_repeat'];
if(empty($Name) || empty($Email) || empty($Password) || empty($PasswordRepeat)){
header("Location: ../signup.php?error=emptyfields=1"); //Check if any field is empty
exit();
}
else if(!filter_var($Email, FILTER_VALIDATE_EMAIL) && !preg_match("/^[a-zA-Z0-9]*$/", $Name)){
header("Location: ../signup.php?error=invalidamil&uid"); //Check if username and email is valid input
exit();
}
else if(!filter_var($Email, FILTER_VALIDATE_EMAIL)){
header("Location: ../signup.php?error=invalidamil&uid=".$Name); //Check if email is valid input
exit();
}
else if($Password !== $PasswordRepeat){
header("Location: ../signup.php?error=passwordCheck&uid=".$Name."&mail=".$Email); // Check if passwords don't match
exit();
}
$sql2 = "SELECT UserName FROM dbo.MainTable WHERE UserName = ?";
$params2 = array($Name, SQLSRV_PARAM_IN);
$stmt2 = sqlsrv_query($conn, $sql2, $params2);
if($stmt2 === false)
{
die(print_r(sqlsrv_errors(), true));
exit();
}
$row_count = sqlsrv_num_rows($stmt2);
if($row_count != 0)
{
$_SESSION['errMsg'] = "Error retrieving username";
header("location: ../register.php");
exit();
}
else if($row_count > 0)
{
$_SESSION['errMsg'] = "Username is already used";
header("Location: ../signup.php?error=UserNameTaken&uid");
exit();
}
else{
$sql = "INSERT INTO dbo.MainTable(UserName,Email,UserPassword)
VALUES (?,?,?)";
$Password = PASSWORD_HASH($_POST['pwd'], PASSWORD_DEFAULT); //Password hashing
$stmt = sqlsrv_query($conn, $sql,array(#$Name,#$Email,#$Password));
if($stmt === false){
die( print_r( sqlsrv_errors(), true));
}else{
$_SESSION['errMsg'] = "Registration completed!";
header("Location: ../signup.php?signup=COMPLETE");
exit();
}
}
I am not sure where to put a change message variable here because I couldn't get it work in the if statements.

Answer 1

You are providing the error message as an url paramenter, so you can access it with php $_GET
<h3>
<?php
echo $_GET['error'];
?>
<h3>