concatenation in php

<?php
 header('Refresh: 60');
 $first_name='pravin';
 $last_name='mishra';
?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Untitled Document</title>
</head>

<body>
<h1>My Full Name</h1>
<?php
echo $table_name=$first_name.' kumar '.$last_name;
?>
</body>
</html>