Php Web form Message Gone After Error - php

Question

my web form work fine, except
if user submit the form with 1 or more field missing
user will see error message and all the input/message gone.
user will have to type the message again
1) How to keep the message so user don't have to type again?
2) is my web form secure from spammer?
my web form
http://www.jewelryindonesia.com/contact.php
my form code:
<?php
// check for a successful form post
if (isset($_GET['s'])) echo "<div class=\"alert alert-success\">".$_GET['s']."</div>";
// check for a form error
elseif (isset($_GET['e'])) echo "<div class=\"alert alert-danger\">".$_GET['e']."</div>";
?>
<form role="form" method="POST" action="contact-form-submission.php">
<div class="row">
<div class="form-group col-lg-4">
<label for="input1">Name</label>
<input type="text" name="contact_name" class="form-control" id="input1">
</div>
<div class="form-group col-lg-4">
<label for="input2">Email Address</label>
<input type="email" name="contact_email" class="form-control" id="input2">
</div>
<div class="form-group col-lg-4">
<label for="input3">Phone Number/WhatsApp</label>
<input type="phone" name="contact_phone" class="form-control" id="input3">
</div>
<div class="clearfix"></div>
<div class="form-group col-lg-12">
<label for="input4">Message</label>
<textarea name="contact_message" class="form-control" rows="6" id="input4"></textarea>
</div>
<div class="form-group col-lg-12">
<input type="hidden" name="save" value="contact">
<button type="submit" class="btn btn-primary">Submit</button>
</div>
</div>
</form>
my php:
<?php
// check for form submission - if it doesn't exist then send back to contact form
if (!isset($_POST['save']) || $_POST['save'] != 'contact') {
header('Location: contact.php'); exit;
}
// get the posted data
$name = $_POST['contact_name'];
$email_address = $_POST['contact_email'];
$phone = $_POST['contact_phone'];
$message = $_POST['contact_message'];
// check that a name was entered
if (empty($name))
$error = 'You must enter your name.';
// check that an email address was entered
elseif (empty($email_address))
$error = 'You must enter your email address.';
// check for a valid email address
elseif (!preg_match('/^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$/', $email_address))
$error = 'You must enter a valid email address.';
// check that a phone number was entered
if (empty($phone))
$error = 'You must enter your phone number.';
// check that a message was entered
elseif (empty($message))
$error = 'You must enter a message.';
// check if an error was found - if there was, send the user back to the form
if (isset($error)) {
header('Location: contact.php?e='.urlencode($error)); exit;
}
$headers = "From: $email_address\r\n";
$headers .= "Reply-To: $email_address\r\n";
// write the email content
$email_content = "Name: $name\n";
$email_content .= "Email Address: $email_address\n";
$email_content .= "Phone Number: $phone\n";
$email_content .= "Message:\n\n$message";
// send the email
//ENTER YOUR INFORMATION BELOW FOR THE FORM TO WORK!
mail ('xxxx#gmail.com', 'Jewelryxxx.com Online Form', $email_content, $headers);
// send the user back to the form
header('Location:jewelry-indonesia-thankyou.html?s='.urlencode('Your Message Has Been Sent ! Thank you for your message.')); exit;
?>

Answer 1

To avoid user don't have to type again when your script jump into error validation, you can store $_POST field to a variable, then call again that variable on html field value.
Web form spammer can be avoided by placing capcha and more validation input, as mentioned above simply can be ussing isset.
isset($_POST['keterangan']) for example
!isset() and $_POST[var]==""; same meaning
EDIT all proccess on 1 page code contact.php
<?php
$name = $_POST['contact_name'];
$email_address = $_POST['contact_email'];
$phone = $_POST['contact_phone'];
$message = $_POST['contact_message'];
if ($name=="" || $email_address="" || $phone=="" || $message==""){
if ($_POST['save']=="contact"){
echo "semua field harus diisi untuk melanjutkan";
}
}else{
// check that a name was entered
if (empty($name))
$error = 'You must enter your name.';
// check that an email address was entered
elseif (!isset($email_address))
$error = 'You must enter your email address.';
// check for a valid email address
elseif (preg_match("/^[_a-z0-9-]+(\.[_a-z0-9-]+)*#[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$/", $email_address))
$error = 'You must enter a valid email address.';
// check that a phone number was entered
if (empty($phone))
$error = 'You must enter your phone number.';
// check that a message was entered
elseif (empty($message))
$error = 'You must enter a message.';
// check if an error was found - if there was, send the user back to the form
if (isset($error)) {
echo "<div class=\"alert alert-danger\">".$error."</div>";
}else{
$headers = "From: $email_address\r\n";
$headers .= "Reply-To: $email_address\r\n";
$email_content = "Name: $name\n";
$email_content .= "Email Address: $email_address\n";
$email_content .= "Phone Number: $phone\n";
$email_content .= "Message:\n\n$message";
mail ('xxxx#gmail.com', 'Jewelryxxx.com Online Form', $email_content, $headers);
// send the user back to the form
echo "<div class=\"alert alert-success\">Your Message Has Been Sent ! Thank you for your message.</div>";
}
}
echo '<form role="form" method="POST" action="contact.php">
<div class="row">
<div class="form-group col-lg-4">
<label for="input1">Name</label>
<input type="text" name="contact_name" class="form-control" id="input1" value="'.$name.'">
</div>
<div class="form-group col-lg-4">
<label for="input2">Email Address</label>
<input type="email" name="contact_email" class="form-control" id="input2" value="'.$email_address.'">
</div>
<div class="form-group col-lg-4">
<label for="input3">Phone Number/WhatsApp</label>
<input type="phone" name="contact_phone" class="form-control" id="input3" value="'.$phone.'">
</div>
<div class="clearfix"></div>
<div class="form-group col-lg-12">
<label for="input4">Message</label>
<textarea name="contact_message" class="form-control" rows="6" id="input4">'.$message.'</textarea>
</div>
<div class="form-group col-lg-12">
<input type="hidden" name="save" value="contact">
<button type="submit" class="btn btn-primary">Submit</button>
</div>
</div>
</form>';
?>