Why is my PHP code is not inserting:

<pre>

<?php

		 
		if(isset($_POST['enter']))
		{
				//capture the variable from the form and store in php variables
			 
			
			$title=$_POST['title'];
			$firstname=$_POST['firstname'];
			$lastname=$_POST['lastname'];
			$username=$_POST['username'];
			$email=$_POST['email'];
			$gender=$_POST['gender'];
			
			$address=$_POST['address'];
			$mypwd=$_POST['mypwd'];
			
			
			
			include'db_server.php';
			
			//select the database you want to query
			
			$sql="SELECT * FROM members WHERE username='$username'";
			$result= mysqli_query($conn, $sql) or die ("ERROR:" .mysqli_error());
			$rowcount=mysqli_num_rows($result);
			
			if($rowcount >= 1) //checking to see if usernamename is already exist
			{
				 echo "<script type=\"text/javascript\">
					  alert('Username already exits');
					  window.location=\"../login_user.html\";
					   </script>";
			}
			else
			{
				//insert data into table
				
				$sql = "INSERT INTO members
				VALUES('$title', '$firstname', '$lastname', '$username', '$email', '$gender', '$address', md5('$mypwd'))";
			
				if(mysqli_query($conn,$sql))
				{
					mysqli_close($conn);
					
					echo "<script type=\"text/javascript\">
					  alert('Username already exits');
					  window.location=\"../index.html\";
					   </script>";
							
				}
				else
				{
					echo "Error inserting values into database";
				}
				//end of line
				
			}
		}	
		
			
?>