I cant insert data in my database.Quick help Please

<?php include_once('include/config.php'); if(isset($_POST['submit'])) { $fname=$_POST['full_name']; $address=$_POST['address']; $city=$_POST['city']; $gender=$_POST['gender']; $email=$_POST['email']; $password=md5($_POST['password']); $query=mysql_query("insert into users(full_name,address,city,gender,email,password) values('$fname','$address','$city','$gender','$email','$password')"); if($query) { echo ""; //header('location:user-login.php'); } } ?>
<head>
	<title>User Registration</title>
	<meta charset="utf-8" />
	<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=0, minimum-scale=1.0, maximum-scale=1.0">
	<meta name="apple-mobile-web-app-capable" content="yes">
	<meta name="apple-mobile-web-app-status-bar-style" content="black">
	<meta content="" name="description" />
	<meta content="" name="author" />
	<link href="http://fonts.googleapis.com/css?family=Lato:300,400,400italic,600,700|Raleway:300,400,500,600,700|Crete+Round:400italic" rel="stylesheet" type="text/css" />
	<link rel="stylesheet" href="vendor/bootstrap/css/bootstrap.min.css">
	<link rel="stylesheet" href="vendor/fontawesome/css/font-awesome.min.css">
	<link rel="stylesheet" href="vendor/themify-icons/themify-icons.min.css">
	<link href="vendor/animate.css/animate.min.css" rel="stylesheet" media="screen">
	<link href="vendor/perfect-scrollbar/perfect-scrollbar.min.css" rel="stylesheet" media="screen">
	<link href="vendor/switchery/switchery.min.css" rel="stylesheet" media="screen">
	<link rel="stylesheet" href="assets/css/styles.css">
	<link rel="stylesheet" href="assets/css/plugins.css">
	<link rel="stylesheet" href="assets/css/themes/theme-1.css" id="skin_color" />
	
	
	

</head>

<body class="login">
	<!-- start: REGISTRATION -->
	<div class="row">
		<div class="main-login col-xs-10 col-xs-offset-1 col-sm-8 col-sm-offset-2 col-md-4 col-md-offset-4">
			<div class="logo margin-top-30">
			<h2>Patient Registration</h2>
			</div>
			<!-- start: REGISTER BOX -->
			<div class="box-register">
				<form name="registration" id="registration"  method="post">
					<fieldset>
						<legend>
							Sign Up
						</legend>
						<p>
							Enter your personal details below:
						</p>
						<div class="form-group">
							<input type="text" class="form-control" name="full_name" placeholder="Full Name" required>
						</div>
						<div class="form-group">
							<input type="text" class="form-control" name="address" placeholder="Address" required>
						</div>
						<div class="form-group">
							<input type="text" class="form-control" name="city" placeholder="City" required>
						</div>
						<div class="form-group">
							<label class="block">
								Gender
							</label>
							<div class="clip-radio radio-primary">
								<input type="radio" id="rg-female" name="gender" value="female" >
								<label for="rg-female">
									Female
								</label>
								<input type="radio" id="rg-male" name="gender" value="male">
								<label for="rg-male">
									Male
								</label>
							</div>
						</div>
						<p>
							Enter your account details below:
						</p>
						<div class="form-group">
							<span class="input-icon">
								<input type="email" class="form-control" name="email" id="email" onBlur="userAvailability()"  placeholder="Email" required>
								<i class="fa fa-envelope"></i> </span>
								 <span id="user-availability-status1" style="font-size:12px;"></span>
						</div>
						<div class="form-group">
							<span class="input-icon">
								<input type="password" class="form-control" id="password" name="password" placeholder="Password" required>
								<i class="fa fa-lock"></i> </span>
						</div>
						<div class="form-group">
							<span class="input-icon">
								<input type="password" class="form-control" name="password_again" placeholder="Password Again" required>
								<i class="fa fa-lock"></i> </span>
						</div>
						<div class="form-group">
							<div class="checkbox clip-check check-primary">
								<input type="checkbox" id="agree" value="agree">
								<label for="agree">
									I agree
								</label>
							</div>
						</div>
						<div class="form-actions">
							<p>
								Already have an account?
								<a href="user-login.php">
									Log-in
								</a>
							</p>
							<button type="submit" class="btn btn-primary pull-right" id="submit" name="submit">
								Submit <i class="fa fa-arrow-circle-right"></i>
							</button>
						</div>
					</fieldset>
				</form>

				<div class="copyright">
					&copy; <span class="current-year"></span><span class="text-bold text-uppercase"> HMS</span>. <span>All rights reserved</span>
				</div>

			</div>

		</div>
	</div>
	<script src="vendor/jquery/jquery.min.js"></script>
	<script src="vendor/bootstrap/js/bootstrap.min.js"></script>
	<script src="vendor/modernizr/modernizr.js"></script>
	<script src="vendor/jquery-cookie/jquery.cookie.js"></script>
	<script src="vendor/perfect-scrollbar/perfect-scrollbar.min.js"></script>
	<script src="vendor/switchery/switchery.min.js"></script>
	<script src="vendor/jquery-validation/jquery.validate.min.js"></script>
	<script src="assets/js/main.js"></script>
	<script src="assets/js/login.js"></script>
	<script>
		jQuery(document).ready(function() {
			Main.init();
			Login.init();
		});
	</script>
	
<script>

function userAvailability() {
$("#loaderIcon").show();
jQuery.ajax({
url: “check_availability.php”,
data:‘email=’+$("#email").val(),
type: “POST”,
success:function(data){
$("#user-availability-status1").html(data);
$("#loaderIcon").hide();
},
error:function (){}
});
}

</body>
<!-- end: BODY -->

First off, use the code tags when posting code. As for your code, get rid of it. It is obsolete and has been completely removed from Php. It is also very dangerous insecure code. If you have it on the net, remove it immediately. You need to use PDO with prepared statements. https://phpdelusions.net/pdo

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