addcompany.php

<?php

//To Handle Session Variables on This Page
session_start();

//Including Database Connection From db.php file to avoid rewriting in all files
require_once("db.php");

//If user clicked register button
if(isset($_POST)) {

	//Escape Special Characters In String First
	$companyname = mysqli_real_escape_string($conn, $_POST['companyname']);
	$headofficecity = mysqli_real_escape_string($conn, $_POST['headofficecity']);
	$contactno = mysqli_real_escape_string($conn, $_POST['contactno']);
	$website = mysqli_real_escape_string($conn, $_POST['website']);
	$companytype = mysqli_real_escape_string($conn, $_POST['companytype']);
	$email = mysqli_real_escape_string($conn, $_POST['email']);
	$password = mysqli_real_escape_string($conn, $_POST['password']);

	$country = mysqli_real_escape_string($conn, $_POST['country']);
	$state = mysqli_real_escape_string($conn, $_POST['state']);
	$city = mysqli_real_escape_string($conn, $_POST['city']);

	//Encrypt Password
	$password = base64_encode(strrev(md5($password)));

	//sql query to check if email already exists or not
	$sql = "SELECT email FROM company WHERE email='$email'";
	$result = $conn->query($sql);

	//if email not found then we can insert new data
	if($result->num_rows == 0) {

		//sql new registration insert query
		$sql = "INSERT INTO company(companyname, headofficecity, country, state, city, contactno, website, companytype, email, password) VALUES ('$companyname', '$headofficecity', '$country', '$state', '$city', '$contactno', '$website', '$companytype', '$email', '$password')";

		if($conn->query($sql)===TRUE) {

			//If data inserted successfully then Set some session variables for easy reference and redirect to company login
			$_SESSION['registerCompleted'] = true;
			header("Location: company-login.php");
			exit();

		} else {
			//If data failed to insert then show that error. Note: This condition should not come unless we as a developer make mistake or someone tries to hack their way in and mess up :D
			echo "Error " . $sql . "<br>" . $conn->error;
		}
	} else {
		//if email found in database then show email already exists error.
		$_SESSION['registerError'] = true;
		header("Location: company-register.php");
		exit();
	}

	//Close database connection. Not compulsory but good practice.
	$conn->close();

} else {
	//redirect them back to register page if they didn't click register button
	header("Location: company-register.php");
	exit();
}