PHP Form sends Email even if Email and Name are invalid - php

Question

Hi everyone and thanks for your time!
Although it's the first time that I try PHP, I've been making a PHP Form and so far I've been able to make it validate the fields, and also that the form doesn't send anything if the fields are empty.
Now... The fields "Name" and "Email" have validation filters...
"Name" doesn't allow more than "letters and white spaces" and "Email" doesn't allow an "invalid Email format".
Example:
Name: Rob3rt... it has a number
Email: anything... isn't an Email address
Subject and Message have no validation filters...
The problem is, that if I fill up all fields, the form sends the Email, even if the information written on "Name" and "Email" doesn't agree with their validation filters...
Q: How can I hold the form from sending an Email, until all fields have the correct information inside?
Here's the code:
// This is the validation code //
<?php
// define variables and set to empty values
$nameErr = $emailErr = $commentErr = $subjectErr = "";
$name = $email = $comment = $subject = "";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["name"])) {
$nameErr = "<h5>Name is required</h5>";
} else {
$name = test_input($_POST["name"]);
// check if name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$nameErr = "<h5>Only letters and white space allowed</h5>";
}
}
if (empty($_POST["email"])) {
$emailErr = "<h5>Email is required</h5>";
} else {
$email = test_input($_POST["email"]);
// check if e-mail address is well-formed
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "<h5>Invalid email format</h5>";
}
}
if (empty($_POST["comment"])) {
$commentErr = "<h5>Message is required</h5>";
} else {
$comment = test_input($_POST["comment"]);
}
if (empty($_POST["subject"])) {
$subjectErr = "<h5>Subject is required</h5>";
} else {
$subject = test_input($_POST["subject"]);
}
}
function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
<form>
Form comes here
</form>
// This is the sending code... I think the problem is here... //
<?php
if($_POST['name']!="" && $_POST['email']!="" && $_POST['comment']!="" && $_POST['subject']!="") {
$to = "myemail#whatever.com";
$email = "From: " . $email . "\r\n";
$subject = "" . $subject . "\r\n";
$comment = "" . $comment . "\r\n";
mail($to,$subject,$comment,$email);
echo "good";
}
else {
"bad";
}
?>

Answer 1

It is not working, because you never check if an error occurred, you are only checking if the fields are not empty before you send the mail.
The simplest way to fix it is replacing
if($_POST['name']!="" && $_POST['email']!="" && $_POST['comment']!="" && $_POST['subject']!="") {
with
if ($_SERVER['REQUEST_METHOD'] === 'POST' && $nameErr === '' && $emailErr === '' && $commentErr === '' && $subjectErr === '') {
There is no no need to check for empty fields again, you have already done it before, so you just need to check if you are POSTing the form and if all errors are empty.
Some advice on how to generally improve your code:
1) Do not handle the HTTP POST in two positions (once above the form and once below). Merge it together in one PHP code block.
2) At least make sure that the user can't re-submit a successful form by reloading the site. After a successful submit, redirect the page. Something like this:
mail($to,$subject,$comment,$email);
header('Location:' . $_SERVER['REQUEST_URI'] . '?status=ok');
exit();
3) separate your HTML from your PHP or you will end up with a huge file which gets hard to maintain. Put your HTML form in a separate file and include it.
Although imho the nicest solution for a form is to sanitize in in JavaScript, submit it via AJAX (with angular, react, jQuery, whatever), handle it (and sanitize the data again) in PHP, send a 4xx HTTP header on error and return the error messages as a JSON object, which you then use in JavaScript.