PHP - Form error alerts displays on page load - php

Question

i am a newbee and just learning along the way. I have two forms on a page (I have only shown one of them as the other form is the same code with different variables). Both their error messages display on page load. How can I stop this?
I have read multiple posts regarding this but I still cannot find a solution.
<?php
if(isset($_POST['Update'])) {
$c_fname = $_POST['fname'];
$c_lname = $_POST['lname'];
$c_email = $_POST['email'];
$c_phone = $_POST['phone'];
// Save $_POST to $_SESSION
//query
$insert_det = "INSERT INTO Cus_acc_details(CUS_Fname,CUS_Lname,Cus_Email,CUS_Phone)
VALUES (?,?,?,?)
ON DUPLICATE KEY
UPDATE
Cus_acc_details.CUS_Fname = '$c_fname',
Cus_acc_details.Cus_Lname = '$c_lname',
Cus_acc_details.Cus_Email = '$c_email',
Cus_acc_details.CUS_Phone = '$c_phone'";
$stmt = mysqli_prepare($dbc, $insert_det);
//new
// $stmt = mysqli_prepare($dbc, $insert_c);
//debugging
//$stmt = mysqli_prepare($dbc, $insert_c) or die(mysqli_error($dbc));
mysqli_stmt_bind_param($stmt, 'sssi', $c_fname, $c_lname, $c_email, $c_phone);
/* execute query */
$r = mysqli_stmt_execute($stmt);
// if inserted echo the following messges
if ($r) {
echo "<script> alert('Saved')</script>";
}
} else {
echo "<b>Oops! we have an issu </b>";
}
?>

Answer 1

You have an else after your if (isset($_POST['Update'])). Inside that else you are displaying errors as if the user tried to submit the form. $_POST['Update'] will only be set if the user tried to submit the form. Move that else inside your if:
if (isset($_POST['Update'])) {
/* a bunch of code to insert into the DB */
// if inserted echo the following messges
if ($r) {
echo "<script> alert('Saved')</script>";
}else{
echo "<b>Oops! we have an issu </b>";
}
}
In Addition:
The commenter is right. You are at risk for SQL Injection. Please use prepared statements instead.

Answer 2

The problem is your else statement is running every time the variable $_POST['Update'] is not set.
One way to fix this is to move your error message inside your form checking code. Something like this would work:
if (isset($_POST['Update'])) {
/* unchanged code snipped */
if ($r) {
echo "<script> alert('Saved')</script>";
} else {
echo "<b>Oops! we have an issu </b>";
}
}
Hope that helps!