PHP Form validation logic is a little off - php

Question

I am validating an HTML Form with PHP. All of my code is fine, except the message field. If I put something in the message field and the other fields are displaying errors, it still submits. But, if I put something into the other fields and the other fields have errors, it won't submit, which is correct. I suspect it has something to do with the last if-else of my code. Thank you in advance.
contact.php
<?php
include 'includes/config.php';
$errors = FALSE;
$displayErrors = NULL;
if (isset($_POST['submit'])) {
$first = $_POST['first'];
$last = $_POST['last'];
$email = $_POST['email'];
$subject = $_POST['subject'];
$message = $_POST['message'];
//Connect to MYSQL Database server
$connect = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die("Could not connect to MYSQL Database.");
$result = mysql_select_db(DB_NAME, $connect) or die("Could not connect to MYSQL table.");
//Clean Data to prevent malicous injections
mysql_real_escape_string(strip_tags(stripcslashes(trim($first))));
mysql_real_escape_string(strip_tags(stripcslashes(trim($last))));
mysql_real_escape_string(strip_tags(stripcslashes(trim($email))));
mysql_real_escape_string(strip_tags(stripcslashes(trim($subject))));
mysql_real_escape_string(strip_tags(stripcslashes(trim($message))));
if (empty($first)) {
$errors = TRUE;
$displayErrors .= 'First name is invalid.<br/>';
}
if (empty($last)) {
$errors = TRUE;
$displayErrors .= 'Last name is invalid.<br/>';
}
if (empty($email) || !filter_var($email, FILTER_VALIDATE_EMAIL)) {
$errors = TRUE;
$displayErrors .= 'Email is invalid.<br/>';
}
if (empty($subject)) {
$errors = TRUE;
$displayErrors .= 'Subject is invalid.<br/>';
}
if (empty($message)) {
$errors = TRUE;
$displayErrors .= 'Message is invalid.<br/>';
} else {
$errors = FALSE;
//Database insertion goes here
echo 'Form submission successful. Thank you ' . $first . '.';
}
}
?>

Answer 1

Basically you are saying, if the message is not empty then $errors=FALSE, but you don't take into account all the other fields.
I'd suggest putting the errors in an array like:
$errors['email'] = true;
Then checking that array at the end using a foreach

Answer 2

Try turning that else into
if($errors == FALSE) {//just corrected the equality operator
//Database insertion goes here
echo 'Form submission successful. Thank you ' . $first . '.'
}

Answer 3

Before all of those ifs, you should put $errors = FALSE. Then instead of the else at the end of your code, you can put if(!$errors){ //database insertion here }

Answer 4

Make all your ifs else ifs
that way your last else will not mess up your validation.

Answer 5

First off, Don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO or MySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.
I've tidied your logic, instead of using $error=true ect you should build an error array (containing your error text) and then check if thats empty at the end, I also cleaned up the magic quotes problem it seems your having, and the horrid multiple mysql_real_escape_string's, hope it helps
contact.php
<?php
include 'includes/config.php';
//Connect to MYSQL Database server
$connect = mysql_connect(DB_HOST, DB_USER, DB_PASS) or die("Could not connect to MYSQL Database.");
$result = mysql_select_db(DB_NAME, $connect) or die("Could not connect to MYSQL table.");
$errors = array();
if ($_SERVER['REQUEST_METHOD']=='POST') {
function clean(&$value){
if (get_magic_quotes_gpc()){
$value = mysql_real_escape_string(strip_tags(trim($value)));
}else{
$value = mysql_real_escape_string(trim($value));
}
}
array_walk($_POST,'clean');
if (empty($_POST['first'])) {
$errors['first']= 'First name is invalid.<br/>';
}else{
$first = $_POST['first'];
}
if (empty($_POST['last'])) {
$errors['last']= 'Last name is invalid<br/>';
}else{
$last = $_POST['last'];
}
if (empty($_POST['email']) || !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)) {
$errors['email'] = 'Email is invalid.<br/>';
}else{
$email = $_POST['email'];
}
if (empty($_POST['subject'])) {
$errors['subject']= 'Subject is invalid.<br/>';
}else{
$subject = $_POST['subject'];
}
if (empty($_POST['message'])) {
$errors['message']= 'Message is invalid.<br/>';
}else{
$message = $_POST['messsage'];
}
if(empty($errors)){
//Database insertion goes here
echo 'Form submission successful. Thank you ' . htmlentities($first) . '.';
}else{
//Errors, so your have $errors['name'] ect to output
//so somthing like:
echo (isset($errors['name'])?$errors['name']:null);
}
}
?>
You should also perhaps add a condition that the value is a min certain length, with strlen($_POST['first']) > 2 ect.