Mysql query fails on remote server but works on xampp - php

Question

i have a php script that works well on xampp server, but when I upload to my online server it fails to execute the mysql_query always. weird part is that it works well offline. the registration script always returns 'failure!' on my online server.
i have downgraded the php version on my server to 5.4 but still no luck.
this is the part of the script that returns the error string:
$test = mysql_query("INSERT INTO users(fname,lname,email,city,gender,password) VALUES('$fname','$lname','$email','$city','$gender','$passwordhash')");
if($test) {
echo "Registration successful";
$last_id = mysql_insert_id();
Registration_WelcomeMessage($fname,$email);
}else{echo "failure!";}
and this is the full code:
<?php
require_once 'db.php';
require_once 'utilities/cleaner.php';
require_once 'reg_welcome_message.php';
if(isset($_POST)){
$broom = new cleaner();
$fname = $broom->clean($_POST['fname']);
$lname = $broom->clean($_POST['lname']);
$email = $broom->clean($_POST['email']);
$city = $broom->clean($_POST['city']);
$gender = $broom->clean($_POST['gender']);
$password = $broom->clean($_POST['password']);
$cpassword = $broom->clean($_POST['cpassword']);
$count = 2;
if ($fname && $lname && $email && $city && $gender && $password && $cpassword) {
if (preg_match("/^[_\.0-9a-zA-Z-]+#([0-9a-zA-Z][0-9a-zA-Z-]+\.)+[a-zA-Z]{2,6}$/i", $email)) {
if (strlen($password) > 5) {
if ($password == $cpassword) {
$remail = mysql_query("SELECT email FROM users WHERE email='$email'");
$checkemail = mysql_num_rows($remail);
if ($checkemail > 0) {
echo "This email is already registered! Please type another email...";
} else {
$passwordhash = hash('sha1',$password);
$test = mysql_query("INSERT INTO users(fname,lname,email,city,gender,password) VALUES('$fname','$lname','$email','$city','$gender','$passwordhash')");
if($test) {
echo "Registration successful";
$last_id = mysql_insert_id();
Registration_WelcomeMessage($fname,$email);
}else{echo "failure!";}
}
} else {
echo "Your passwords don't match!";
}
} else {
echo "Your password is too short! A password between 6 and 15 charachters is required!";
}
}else{
echo "Please use a valid email!";
}
} else {
echo "You have to complete the form!";
}
}else{echo "NO data sent";}
?>